WASHINGTON — President Bush was told more than a month before the attacks of Sept. 11, 2001, that supporters of Osama bin Laden planned an attack within the United States with explosives and wanted to hijack airplanes, a government official said Friday.

The disclosure appears to contradict the White House's repeated assertions that the briefing the president received about the Qaeda threat was "historical" in nature and that the White House had little reason to suspect a Qaeda attack within American borders.

The warning came in a secret briefing that Mr. Bush received at his ranch in Crawford, Tex., on Aug. 6, 2001. A report by a joint Congressional committee last year alluded to a "closely held intelligence report" that month about the threat of an attack by Al Qaeda, and the official confirmed an account by The Associated Press on Friday saying that the report was in fact part of the president's briefing in Crawford.

The disclosure appears to contradict the White House's repeated assertions that the briefing the president received about the Qaeda threat was "historical" in nature and that the White House had little reason to suspect a Qaeda attack within American borders.

Members of the independent commission investigating the Sept. 11 attacks have asked the White House to make the Aug. 6 briefing memorandum public. The A.P. account of it was attributed to "several people who have seen the memo." The White House has said that nothing in it pointed specifically to the kind of attacks that actually took place a month later.

The Congressional report last year, citing efforts by Al Qaeda operatives beginning in 1997 to attack American soil, said that operatives appeared to have a support structure in the United States and that intelligence officials had "uncorroborated information" that Mr. bin Laden "wanted to hijack airplanes" to gain the release of imprisoned extremists. It also said that intelligence officials received information in May 2001, three months earlier, that indicated "a group of bin Laden supporters was planning attacks in the United States with explosives."

Also on Friday, the White House offered evidence that the Federal Bureau of Investigation received instructions more than two months before the Sept. 11 attacks to increase its scrutiny of terrorist suspects inside the United States. But it is unclear what action, if any, the bureau took in response.

The disclosure appeared to signal an effort by the White House to distance itself from the F.B.I. in the debate over whether the Bush administration did enough in the summer of 2001 to deter a possible terrorist attack in the United States in the face of increased warnings.

A classified memorandum, sent around July 4, 2001, to Condoleezza Rice, the president's national security adviser, from the counterterrorism group run by Richard A. Clarke, described a series of steps it said the White House had taken to put the nation on heightened terrorist alert. Among the steps, the memorandum said, "all 56 F.B.I. field offices were also tasked in late June to go to increased surveillance and contact with informants related to known or suspected terrorists in the United States."

Parts of the White House memorandum were provided to The New York Times on Friday by a White House official seeking to bolster the public account provided a day before by Ms. Rice, who portrayed an administration aggressively working to deter a domestic terror attack.

But law enforcement officials said Friday that they believed that Ms. Rice's testimony before the commission investigating the Sept. 11 attacks — including her account of scores of F.B.I. investigations under way that summer into suspected Qaeda cells operating in the United States — overstated the scope, thrust and intensity of activities by the F.B.I. within American borders.

Agents at that time were focused mainly on the threat of overseas attacks, law enforcement officials said. The F.B.I. was investigating numerous cases that involved international terrorism and may have had tangential connections to Al Qaeda, but one official said that despite Ms. Rice's account, the investigations were focused more overseas and "were not sleeper cell investigations."

The finger-pointing will probably increase next week when numerous current and former senior law enforcement officials, including Attorney General John Ashcroft, testify before the Sept. 11 commission. In an unusual pre-emptive strike, Mr. Ashcroft's chief spokesman on Friday accused some Democrats on the commission of having "political axes to grind" in attacking the attorney general, who oversees the F.B.I., and unfairly blaming him for law enforcement failures.

A similar accusation against the commission was also leveled by Senator Mitch McConnell, a Kentucky Republican with ties to the White House, in a speech on the Senate floor Thursday.

"Sadly, the commission's public hearings have allowed those with political axes to grind, like Richard Clarke, to play shamelessly to the partisan gallery of liberal special interests seeking to bring down the president," Mr. McConnell said.

The charges and countercharges underscored the political challenge that the investigation into the Sept. 11 attacks has become for President Bush as he mounts his re-election bid. The White House sought this week to defuse the situation by allowing Ms. Rice to testify before the Sept. 11 commission after months of resistance. But her appearance served to raise new questions about the administration's efforts to deter an attack.

The White House on Friday put off a decision on declassifying the document at the center of the debate — the Aug. 6 briefing, titled "Bin Laden Determined to Attack Inside the United States." But the administration appeared ready to release at least portions of the document publicly in the coming days.

The memo from Mr. Clarke's group in July 2001 about F.B.I. activities adds another piece of evidence to the document trail, but it is unlikely to resolve the questions over whether the administration did enough to deter an attack.

White House officials, who spent several weeks attacking Mr. Clarke's credibility, said Friday that they believed the memo from his counterterrorism group was an accurate reflection of steps the White House took to deter an attack. But they questioned whether the F.B.I. executed the instructions to intensify its scrutiny of terrorist suspects and contacts in the United States.

In April 2001, the F.B.I. did send out a classified memo to its field offices directing agents to "check with their sources on any information they had relative to terrorism," said a senior law enforcement official who spoke on condition of anonymity. But with the level of threat warnings increasing markedly over the next several months, there is no indication that any directive went out in the late June period that was described in the memo from Mr. Clarke's office.

That summer saw a string of alerts by the F.B.I. and other government agencies about the heightened possibility of a terrorist attack, but most counterterrorism officials believed an attack would come in Saudi Arabia, Israel or elsewhere. Many also were worried about a July 4 attack and were relieved when that date passed uneventfully.

For months, the F.B.I. had been consumed by internal problems of its own, including the arrest of an agent, Robert P. Hanssen, on espionage charges, the disappearance of documents in the Oklahoma City bombing case and the fallout over the Wen Ho Lee spy case. Moreover, the bureau was going through a transition in leadership, with its longtime director, Louis J. Freeh, retiring in June 2001. He was replaced by an acting director, Thomas J. Pickard, until the current director, Robert S. Mueller III, took over in September, just days before the deadly hijackings. All three men will testify at next week's commission hearings and are expected to face sharp questioning about whether the F.B.I. did enough to prevent an attack in the weeks and months before Sept. 11.

At this week's appearance by Ms. Rice, several commissioners sharply questioned whether the F.B.I. and the Justice Department had done enough to act on intelligence warnings about an attack.

"We have done thousands of interviews here at the 9/11 commission," said Timothy J. Roemer, a Democratic member of the panel. "We have gone through literally millions of pieces of paper. To date, we have found nobody — nobody at the F.B.I. who knows anything about a tasking of field offices" to identify the domestic threat.

The apparent miscommunication will probably be a central focus of the commission's hearing next week. Scrutiny is expected to focus in part on communication breakdowns between the F.B.I. and the C.I.A. that allowed two of the 19 hijackers to live openly in San Diego despite intelligence about their terrorist ties.

Another Democratic panel member, Jamie S. Gorelick, said at Thursday's hearing that Mr. Ashcroft was briefed in the summer of 2001 about terrorist threats "but there is no evidence of any activity by him."

Such criticism led Mark Corallo, Mr. Ashcroft's chief spokesman at the Justice Department, to say Friday that "some people on the commission are seeking to score political points" by unfairly attacking Mr. Ashcroft's actions before Sept. 11.

"Some have political axes to grind" against Mr. Ashcroft, Mr. Corallo said in an interview, naming Ms. Gorelick, who was the deputy attorney general in the Clinton administration; Mr. Roemer, a former congressman from Indiana, and Richard Ben-Veniste, the former Watergate prosecutor.

While insisting that he was not speaking personally for Mr. Ashcroft, Mr. Corallo said he was offended by Ms. Gorelick's remarks in particular. Offering a detailed preview of Mr. Ashcroft's testimony next week, he said the attorney general was briefed repeatedly by the C.I.A. and the F.B.I. on threats posed by Al Qaeda and was told that the threats were directed at targets overseas. "He was not briefed that there was any threat to the United States," Mr. Corallo said. "He kept asking if there was any action he needed to take, and he was constantly told no, you're doing everything you need to do."

Several commission officials denied in interviews that there was any attempt to treat Mr. Ashcroft unfairly. Al Felzenberg, a spokesman for panel, said that Mr. Ashcroft would be warmly received.

Ms. Gorelick said she was surprised by Mr. Corallo's comments and puzzled by assertions that the attorney general had no knowledge of a domestic terrorist threat in 2001.

"This appears to be a debate within the administration," she said. "On the one hand, you have Dr. Rice saying that the domestic threat was being handled by the Justice Department and F.B.I., and on the other hand, you have the Justice Department saying that there did not appear to be a domestic threat to address. And that is a difference in view that we have to continue to explore."

The commission also heard testimony Friday morning behind closed doors from former Vice President Al Gore.

Former President Bill Clinton appeared before the panel in closed session on Thursday, but a Democratic commission member took issue Friday with Mr. Clinton's assertion that that there was not enough intelligence linking Al Qaeda to the 2000 bombing of the Navy destroyer Cole to justify a military attack on the terrorist organization.

"I think he did have enough proof to take action," Bob Kerrey, the former senator from Nebraska, said on ABC's `Good Morning America.'

Philip Shenon, Adam Nagourney and James Risen contributed reporting for this article.

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