There is no immediate indication that the tape of the al Qaeda leader, which aired Friday, offered any sign of an impending strike, said a U.S. government official, speaking on condition of anonymity.
Intelligence agencies are conducting further analysis on the tape.
The Bush administration left the terror threat level unchanged.
"We don't have to go to (code level) orange to take action in response either to these tapes or just general action to improve security around the country," Homeland Security Secretary Tom Ridge told reporters Saturday.
Ridge urged Americans to go ahead with plans to vote in Tuesday's elections without undue concern.
His words and appearance both seemed designed to convey a lack of alarm. The nation's top anti-terrorism official made his remarks in casual clothes standing outside his office, rather than at a formal news conference of the type he and other administration officials have conveyed word of increased danger in the past.
The warning from federal authorities shortly before Tuesday's election follows public discussion by top Bush administration officials during the summer about the seriousness of a potential threat to disrupt the election.
"We remain concerned about al Qaeda's interest in attacking the American homeland, and we cannot discount the possibility that the video may be intended to promote violence or serve as a signal for an attack," according to the memo sent late Friday from the FBI and the Homeland Security Department.
The bulletin went to homeland security advisers; federal, state and local law enforcement; and select members of private industry.
The government official said steps have been taken to secure the public and that homeland security officials have been urged to keep vigilant.
The tape, including portions net yet broadcast, contained no overt threat and no specific timetable or method of an attack, according to a law enforcement official, speaking on condition of anonymity.
This official, who was briefed on the entire tape, said much of what has not aired amounts to a sustained diatribe against President Bush and his father, former President George H.W. Bush. It even criticizes the current president's economic and jobs programs and contends that the Iraq war is all about oil, the official said.
Government officials were comparing what bin Laden said with other al Qaeda intelligence gathered to see if patterns emerge that could lead them to a plot or potential terrorist operatives. That includes a tape aired Thursday by ABC News in which a shrouded man claiming to be an American member of al Qaeda promised attacks that will make U.S. streets "run red with blood."
The president on Saturday directed his national security aides to take any necessary steps in response to the bin Laden tape.
Mr. Bush held a videoconference call with national security adviser Condoleezza Rice and the heads of the CIA, FBI and departments of Justice and Homeland Security.
White House spokesman Scott McClellan said the president directed them to make sure any necessary action is taken with regard to the tape.
McClellan did not say what steps were being taken or contemplated. He played down the possibility of the administration raising the threat advisory level, currently at "yellow," or elevated, for most of the country.
Also Saturday, several hundred homeland security officials and some police chiefs held a conference call to discuss the tapes. Security at polling places on Tuesday was among the concerns and questions they raised.
In the video, bin Laden acknowledged for the first time directly that he ordered the Sept. 11 attacks and said he did so because of injustices against the Lebanese and Palestinians by Israel and the United States.
He said the United States must stop threatening the security of Muslims if it wants to avoid "another Manhattan" and while he did not directly warn of new attacks, he warned: "There are still reasons to repeat what happened."
"Your security is not in the hands of Kerry, Bush or al Qaeda. Your security is in your own hands," bin Laden said, referring to the president and his Democratic opponent, John Kerry. "Any state that does not mess with our security has naturally guaranteed its own security."
The television network Al-Jazeera received the 18-minute videotape at its offices in the Pakistani capital, Islamabad, where "somebody dropped it yesterday at the gate," Ahmad Muaffaq Zaidan, the Pakistan bureau chief, said Saturday.
In the earlier tape, the speaker who identifies himself as "Azzam the American" praised the Sept. 11 attacks, called bin Laden and his deputy his leaders, and said a new wave of attacks could come at any moment.
The U.S. military in Afghanistan on Saturday dismissed the tape as "propaganda," and insisted that the al Qaeda leader would be caught — but acknowledged having no fix on his whereabouts.
Spokesman Maj. Scott Nelson defended the failure to capture bin Laden in the three years since the Sept. 11, 2001, attacks in America, saying the border area with Pakistan where he might be hiding was mountainous and stretched 1,500 miles. "He can hide pretty much anywhere," Nelson told a news conference.
"The tape is nothing more than propaganda," Nelson said. "If you look at al Qaeda, their organization is being taken down piece-by-piece.
"Although we don't have a timeframe for when bin Laden will be captured, we have full confidence that he will be," the spokesman said.
Asked where bin Laden was hiding, Nelson said the military still suspects he could be somewhere near the Afghan-Pakistani border. "If we knew exactly where he was, we would be there in a moment and we would have a very happy day and a happy election," he said.
Pundits say the political impact of the tape could cut both ways. It bolsters Mr. Bush's argument that the world is a dangerous place and plays to his strength as commander in chief in fighting the war on terror, but it also underscores that his administration has failed to capture or kill America's No. 1 enemy more than three years after the terror attacks on New York and Washington.
Staunch U.S. ally Australia responded to the new tape by underlining its resolve to "confront and defeat" terrorism, and international experts said the message was a clear attempt to meddle with the U.S. election.
"Whenever he says these things and whenever these Islamic extremists and fanatics say these things our message to them is a simple message, and that is: 'We will defy you and we will defeat you, and countries like Australia must not flinch in the face of these fanatics,"' said Australian Foreign Minister Alexander Downer.
"We must show an utter determination to confront them and defeat them."
In Britain, Prime Minister Tony Blair's office said it was looking at the tape but declined to comment. Charles Kennedy, leader of the opposition Liberal Democrats, said Bin Laden's "cynical attempt to manipulate the U.S. elections must not succeed."
"The democratic process is the surest way to defeat this terrorist," Kennedy said.
Others also saw the tape as an attempt to influence Tuesday's presidential vote.
"Bin Laden shocks U.S," was Saturday's headline in Britain's Financial Times newspaper. "Bin Laden to U.S. Voters: Your Fate Is In Your Hands," said the front page of The Daily Telegraph.
On Web sites devoted to extremist Muslim comment, contributors reacted with glee to the tape, saying it was proof bin Laden was alive and was a "slap" at America.
Montasser el-Zayat, a Cairo-based lawyer who defends Islamic radicals, said the video amounted to an "unprecedented attack on Bush at a very critical time, before the U.S. elections."
Paul Wilkinson, chairman of the Center for the Study of Terrorism and Political Violence at St. Andrew's University in Scotland, called the tape "a very crude but sinister attempt to try to influence the presidential election."
"The U.S. authorities must take the threat of violence seriously," he told the British Broadcasting Corp.
Syrian political analyst Imad Fawzi al-Shueibi noted the videotape marked "a radical turnabout in his style ... with no religious allusions, a matter we had not seen before."
"Bin Laden appeared as if he was teasing Bush, telling him: 'Look, I am here and you did not catch me,"' al-Shueibi told The Associated Press in Damascus.
Diaa Rashwan, a Cairo-based expert on extremist Muslim militants, said bin Laden was trying to influence Americans "to give (Democratic presidential candidate John) Kerry their votes, not Bush."
Many felt the tape would have the opposite result. "Bush supporters are confident the video will be widely seen as an attempt to blackmail the nation into changing course, something that can only play to the advantage of the incumbent," noted Britain's Daily Telegraph.
Wilkinson, the terrorism expert, said it was too early to predict whether it would help either candidate.
"It is certainly a more flagrant form of propaganda than we have seen before in relation to the American public, but it hasn't got a hope of influencing American foreign policy," he said.
"Whoever wins the U.S. election will continue to wage war on al Qaeda and its affiliates ... whoever wins the election is unlikely to cut and run from Iraq because they know that policy would be seen as a defeat."