In a lengthy statement, the IRA ordered an end to all armed activity, effective on Thursday at 11 a.m. EDT. The group said it would pursue its goal of a united Ireland through political activity.

In a joint communique issued after the announcement, the British and Irish governments said the declaration would be "momentous" if the IRA follows through on its promise.

British Prime Minister Tony Blair called the order a "step of unparalleled magnitude," saying he hoped to see the speedy disposal of weapons.

"This may be the day which finally, after all these false dawns and dashed hopes, peace replaced war, politics replaces terror," said Blair.

Britain's minister for Northern Ireland has asked the Independent Monitoring Commission, which monitors paramilitary activity, for a progress report by January.

Irish Prime Minister Bertie Ahern said the decision marks the end of the IRA as a "paramilitary organization" and the beginning of a "new era for all of the people on the island of Ireland."

"If the IRA's words are borne out by verified actions, it will be a momentous and historic development," said Ahern.

The president of the Republic of Ireland, Mary McAleese, said disarmament is a "real opportunity" to rebuild trust and understanding.

Gerry Adams, leader of the IRA's political wing, Sinn Fein, said the announcement clears the way for an independent Ireland and called on Protestant groups to agree to talks.

"There is an enormous responsibility on us to seize this moment and to make Irish freedom a reality," said Adams.

There's been no word from Gen. John de Chastelain, the retired Canadian general leading the international charge for disarmament in Northern Ireland.

Washington cautious

Washington reacted cautiously, saying the move is potentially historic if the words are translated into deeds.

The United States was a key player in the 1998 Good Friday Agreement to maintain the ceasefire and establish a power-sharing government in Northern Ireland.

"We understand that many, especially victims and their families, will be skeptical," said White House spokesperson Scott McClellan.

"They will want to be certain that this terrorism and criminality are indeed things of the past."

Washington's envoy to Northern Ireland, Mitchell Reiss, said he's hopeful he'll soon see a "major act of decommissioning" of weapons.