Within minutes after his arrival in Washington from Scotland, where he'd been at the G-8 summit, Mr. Bush was at the British Embassy to sign a condolence book.
Afterward, he said: "To those who suffer loss of life, we pray for God's blessing. For those who are injured, we pray for fast healing."
The president also laid a wreath at the embassy.
The president described the British people as "steadfast and strong" -- and said Americans have long admired their "great spirit."
Mr. Bush had left Scotland earlier than planned. The final day of the summit was shortened so that British Prime Minister Tony Blair could rush back to London to deal with the aftermath of the attacks.
Mr. Bush is to devote his Saturday radio address to the subject of terrorism and will make a speech on terrorism Monday in Quantico, Va. The war on terrorism was the keystone theme of his re-election campaign and his strongest issue with voters.
On the return flight from Scotland on Air Force One, Mr. Bush discussed possible court nominees with White House Chief of Staff Andy Card. The president had pored over court material on his flight to Europe on Tuesday. The White House did not reveal who was on the list to replace retiring Justice Sandra Day O'Connor.
On Tuesday, Mr. Bush is to meet at the White House with Senate leaders, Democrats as well as Republicans, to discuss the court vacancy. The group is to include Majority Leader Bill Frist, R-Tenn., Minority Leader Harry Reid, D-Nev., and Senate Judiciary Committee Chairman Arlen Specter, R-Pa., and Sen. Patrick Leahy, the ranking Democrat on that panel.
White House press secretary Scott McClellan said Mr. Bush's staff also was making consultative calls with senators.
McClellan declined to say whether Bush had talked with any of the candidates, saying he would not disclose details of the selection process.
Mr. Bush spent three days in Gleneagles, Scotland at the G-8 summit of leaders from Britain, France, Germany, Russia, Italy, Canada, Japan and the United States.
Sen. Kent Conrad, D-N.D., said he was contacted Friday by White House Counsel Harriet Miers, who sought his opinion on a replacement for O'Connor.
Conrad said he told Miers he would support Attorney General Alberto Gonzales for the post, if he is nominated. He also said he suggested the president nominate Kermit Bye, a North Dakota native who sits on the 8th U.S. Circuit Court of Appeals
Bye's nomination would likely not have the support of conservatives. On Friday, the 8th Circuit, in an opinion he wrote, ruled that the Partial-Birth Abortion Ban Act is unconstitutional because it makes no exception for the health of the woman.
Card has contacted several other Democratic senators, including Senate Minority Whip Dick Durbin of Illinois, Edward Kennedy of Massachusetts and Charles Schumer of New York.
Meanwhile, last week's retirement of Sandra Day O'Connor hasn't ended the rumors that another Supreme Court justice may be about to step down.
Many court observers had expected Chief Justice William Rehnquist to announce his retirement last week. And when O'Connor did instead, there was speculation that Rehnquist would wait until this week to make the announcement.
In fact, TV news crews waited three hours in the rain this morning outside his home. When he finally came out, and reporters asked if the retirement rumors were true, he was heard to respond, "That's for me to know, and you to find out."
Rehnquist, who's 80, has been battling thyroid cancer.
Other speculation about a possible retirement focused on justices John Paul Stevens and Ruth Bader Ginsburg.