President Bush praised NATO's role in the war against terror Tuesday and urged the alliance to work harder to reach out to Russia even as it expands into nations once part of the Soviet bloc.

With NATO Secretary-General Lord Robertson at his side, Bush extended U.S. thanks to the alliance for standing by the United States from shortly after the Sept. 11 terror attacks, and for sending its aircraft to help patrol U.S. skies.

"The United States is deeply, deeply grateful for this support," he said. Bush called the alliance "a bulwark in the fight against terror."

Bush and Robertson ignored a shouted question about the crisis in the Middle East, leaving the White House Roosevelt Room immediately after giving their prepared statements.

"On that note, why don't I go buy you a meal?" Bush said, and they walked together to the White House residence for dinner.

Asked his feelings about Israeli Prime Minister Ariel Sharon's defiance of Bush's call for Israel to withdraw from occupied Palestinian cities, the president turned with a faint smile and waved at reporters but did not answer.

Bush and Robertson, joined by Vice President Dick Cheney and Defense Secretary Donald H. Rumsfeld, met for almost an hour. An administration official said they discussed the agenda for this year's NATO summit, in Prague, and at one point Robertson told Bush that NATO's options are "modernization or marginalization," meaning the alliance faces becoming irrelevant if it is not upgraded.

Bush and Robertson talked about further NATO expansion into countries that were formerly allied with the Soviet Union. Bush spoke of an alliance stretching "from the Baltic to the Black Sea."

Now, "NATO must forge a new relationship with Russia," Bush said, with U.S. and NATO flags as a backdrop.

Robertson noted that 53 years ago, the terms of the NATO alliance — including the mandate to consider an attack on one an attack on all — was framed in Washington, D.C.

Robertson said that NATO stood together in facing new challenges and new threats. "We will succeed," he predicted.

It was the fourth time Robertson and the president have met.