"The people of Northern Ireland know the threat of terror, they know the value of peace," Mr. Bush said at a St. Patrick's Day reception in the East Room.
"America is encouraged with the great strides that have been made in implementing the Good Friday (peace) agreement."
Mr. Bush cited the daily business of the Northern Ireland Assembly, and the peaceful work of a new Northern Ireland police force as proof of progress in the province.
Irish Prime Minister Bertie Ahern and Gerry Adams, president of Sinn Fein, the political party associated with the Irish Republican Army, were among those applauding the president at the annual reception.
The pair, along with David Trimble, who leads Northern Ireland's joint Catholic-Protestant government, met privately with Mr. Bush and others in the Oval Office. Reporters were not allowed to cover those discussions.
"The good citizens of Northern Ireland and the leaders here today have demonstrated a fierce determination that the next generation must not grow up amid the 'troubles,'" Mr. Bush said in the East Room, referring to the long-running battle between Catholics and Protestants in the province.
Quoting an Irish proverb, Mr. Bush said continued peacemaking will be difficult — like planting in hard soil.
Asked about criticism that the Bush administration has been too hands-off in the Northern Ireland peace process, Ahern told reporters afterward he does not share that view of the president. "He's absolutely helpful to us," the prime minister said.
Wednesday's reception also gave Mr. Bush another chance to pay tribute to the rescue workers of Sept. 11, reports CBS News Correspondent Mark Knoller.
"We're honored today to have with us some Irish-American firefighters who served our nation so heroically on Sept. 11th," he said.
Every year around St. Patrick's Day, presidents have invited Irish leaders to the White House, which was designed by Irish-born architect James Hoban and modeled after Leinster House in Dublin, and lavishly celebrated U.S.-Irish ties.
Keeping with that tradition, Mr. Bush devoted the bulk of his day to the Irish. In the Roosevelt Room, he accepted from Ahern a crystal bowl heaped with clipped shamrocks. Behind closed doors in the Oval Office, Bush met with Northern Ireland leaders then proceeded to the reception and on to Capitol Hill for the annual "Friends of Ireland" luncheon.
Mr. Bush treated his guests to a traditional greeting — "A hundred thousand welcomes to you all," he said — but in English.
"I'm probably not going to try to say that in Gaelic," he added with a chuckle.
On Saturday, Mr. Bush plans to participate in Chicago's annual St. Patrick's Day parade.