Mr. Bush said it could take days, months or years before the United States and its allies complete the search for terrorist leaders. "We're just on the hunt," Mr. Bush said at a news conference with Pakistani President Pervez Musharraf.
"It doesn't matter how long it takes, Mr. President," Mr. Bush said, nodding to Musharraf.
Mr. Bush didn't directly answer a reporter's question about the whereabouts of bin Laden or Saddam, saying "there are more than two principals at large" and that the United States and its partners were capturing or killing other members of both men's circles.
Musharraf said his government was making extraordinary efforts to track down bin Laden and his lieutenants. For the first time, his military is searching tribal border areas that have not been entered by the army in more than a century.
He called these regions "treacherous" territory.
Musharraf has said he thinks bin Laden may be alive in Pakistan.
But, he told a reporter, "whether Osama bin Laden is here or across the border, your guess, sir, would be as good as mine, so I wouldn't like to venture into a guess."
President Bush credited Musharraf with capturing more than 500 al Qaeda and Taliban leaders, and he called Musharraf "a courageous leader" and a friend of the United States.
On Monday, Pakistani officials announced the arrests of five suspected members of an outlawed militant group blamed for killing Shiite Muslims and the kidnap-slaying of American Wall Street Journal reporter Daniel Pearl.
Mr. Bush also announced that the two countries were signing a new trade and investment agreement and he pledged to work with Congress on a $3 billion assistance project for Pakistan. Further, Mr. Bush said the United States had forgiven $1 billion owed by Pakistan in the last year.
In other developments in the war on terror:
Meantime, the U.S. Embassy in Kenya remains closed. It was shut on Friday after the Pentagon raised the terror threat level in the African nation to "high."
The six — five Tunisians and a Moroccan — were picked up in a series of raids and accused of providing logistical support and financing with the aim of Islamic terrorism, fraud, aiding illegal immigration, possessing false documents among other charges. A seventh suspect is at large.