Bush said Blair was one of the first leaders to call after terrorists hijacked commercial airliners and crashed them into the World Trade Center, the Pentagon and the Pennsylvania countryside on Sept. 11. ''He showed to be a true friend and I appreciate that,'' the president said.

The prime minister was accompanying Bush to the Capitol for the president's address to Congress and the nation. The prime minister traveled to Washington from New York where he and his wife, Cherie, stood with former President Clinton, his wife, Sen. Hillary Clinton, and U.N. Secretary-General Kofi Annan in the front row of St. Thomas Church in Manhattan.

They prayed with about 100 British families who were affected by the Sept. 11 attacks on the World Trade Center and the Pentagon.

''It's perhaps only when you are actually there that the full enormity and horror of what happened comes home to you,'' Blair said in Washington. He recalled the days of World War II when Britain was under attack. ''And there was one nation and one people that, above all, stood side by side with us at that time. And that nation was America, and those people were the American people.''

''And I say to you, we stand side by side with you now, without hesitation,'' the prime minister said.

''This is a struggle that concerns us all, the whole of the democratic and civilized and free world,'' Blair said. ''And we have to do two things very clearly: We have to bring to account those responsible; and then we have to set about at every single level and every way that we can dismantling the apparatus of terror and eradicating the evil of mass terrorism in our world.

''And I know that America and Britain and all our allies will stand united together in that task,'' said the prime minister. ''And I give you, on behalf of our country, our solidarity, our sympathy and support.''

He said there was growing, global support for firm action against terrorist.

''Because this struggle is something that should unite people of all faiths, of all nations, of all democratic, political persuasions. And I believe it will.''