President George W Bush and his top security advisers have been discussing how to respond to Tuesday's attacks on New York's World Trade Center and the Pentagon. Bush for the first time said the United States was "at war" and singled out the Saudi-born dissident Osama bin Laden as the chief suspect.
Bush made clear his intentions ahead of the meeting with his national security advisers at the Camp David presidential retreat, saying: "We will not settle for a token act. Our response must be sweeping, sustained and effective..."
And he asked Americans to be patient "for the conflict will not be short. You will be asked for resolve, for the conflict will not be easy. You will be asked for your strength because the course to victory may be long."
His comments, the strongest yet since Tuesday's attacks, came as rescue workers continued to sift through the wreckage from New York's World Trade Center, which collapsed on Tuesday after two hijacked airliners crashed into the twin towers.
Thousands flee Afghanistan
In Afghanistan, thousands were reported to be fleeing the country in anticipation of a US attack aimed at punishing the country's Taliban rulers for their alleged sheltering of Osama bin Laden.
Bush on Saturday echoed the comments of his secretary of state, Colin Powell, saying bin Laden "is what we would call a prime suspect. If he thinks he can hide from the United States, and our allies, he will be sorely mistaken."
Beyond the media spotlight, US officials continued efforts to build an international coalition to support military action against as yet unspecified targets.
Diplomats said they had secured backing from Pakistan, which borders Afghanistan, for military action, but Islamabad was refusing to comment on US requests to use its airspace, or to close its border with Afghanistan.
Analysts acceding to either of those demands would likely provoke public outrage in Pakistan.
Pakistan's foreign minister, Abdul Sattar, said his government would comply with United Nations Security Council resolutions on the terror attacks, but added that he did not expect Pakistan to take part in military operations outside its borders.
Taliban warns against supporting US
For their part, Afghanistan's Taliban leaders warned Pakistan against cooperating with the US, threatening any of its neighbours with "extraordinary danger" if they helped Washington.
Washington's message to other nations, including Arab and Islamic states, was that must either back the US or risk diplomatic and economic isolation.
India signalled it was ready to let the United States use its military facilities and could provide a large base for any military strike at Afghanistan. But US jets would still have to cross Pakistani air space to reach Afghanistan.
Russia and France voiced caution. Russian President Vladimir Putin said: "We must weigh up our decisions and make them on the basis of proven facts."
Bin Laden, speaking through aides, this week denied involvement in the attacks, but described it as "punishment from Allah".
Death toll climbs
The number of missing in New York's World Trade Center climbed to 4,972, or 255 more than estimated on Friday, according to Police Commissioner, Bernard Kerik.
Remains of 152 people have been recovered and 92 of those have been identified, he added. Only five people have been pulled out alive, two on Tuesday and three on Wednesday.
At least 190 people are believed to have died when hijackers crashed a third plane into the Pentagon near Washington. Forty-five others died in a fourth plane that crashed in Pennsylvania after passengers fought with hijackers and foiled their plan to crash into another landmark building.
The cockpit voice recorder retrieved from the wreckage on Friday evening appeared to be in "fairly good condition", investigators said on Saturday.
The FBI on Friday named 19 hijackers, including seven pilots, who commandeered the four airliners used in Tuesday's terror attacks, sought to question more than 100 people and made the first arrest in the investigation, a witness said to have "material" information on the suicide attacks.
Defence Secretary Donald Rumsfeld activated 35,000 reservists out of 50,000 authorised by Bush to provide "strike-alert" jet fighter protection and perform other duties at domestic military bases.
swissinfo with agencies