WASHINGTON - US President Barack Obama urged Northern Ireland's political factions to keep ignoring those who inspire hate rather than hope, as he marked the 15th anniversary of the Good Friday Agreement.

Obama, who will visit Northern Ireland for the G8 summit in June, said its people had traveled a great distance and traded bullets for ballots and destruction for dialogue since the power-sharing deal was forged.

"There is urgent work still to be done -- and there will be more tests to come," Obama said in a written statement.

"There are still those few who prefer to look backward rather than forward - who prefer to inspire hate rather than hope. The many who have brought Northern Ireland this far must keep rejecting their call."

"On behalf of the American people, I salute the people and leaders of Northern Ireland and the model they have given to others struggling toward peace and reconciliation around the world," Obama said.

Good Friday anniversary

The Good Friday Agreement, reached in April 1998, effectively ended years of violence known as "The Troubles" and enshrined a peaceful framework for dealing with religious and political divisions.

It set up an assembly and executive in Northern Ireland to govern with power shared between warring factions and formalized the relationship between Northern Ireland and the Republic of Ireland and Britain.

Several spates of violence in Northern Ireland between loyalists and nationalists this year have prompted warnings by leading politicians that dissident extremists will not be allowed to disturb the hard won peace.

Mr. Obama also paid tribute to Northern Ireland leaders last week.