The Irish Republican Army (search) renounced violence as a political weapon Thursday and said it will resume disarmament, taking a dramatic step designed to revive Northern Ireland (search) peace efforts after a 35-year conflict that killed and maimed thousands.

British Prime Minister Tony Blair (search) called the move "a step of unparalleled magnitude," while Prime Minister Bertie Ahern of Ireland said it heralded "the end of the IRA as a paramilitary organization." The White House also welcomed the announcement.

But local leaders in the British territory and some analysts warned that the IRA, which has previously fallen short on fulfilling its public promises, had left key questions unanswered and was not disbanding.

The IRA said all its clandestine units had been ordered to dump arms and cease all activities, as of 4 p.m. (11 a.m. EDT) Thursday.

"The leadership has formally ordered an end to the armed campaign," the IRA said in a major advance from its opened-ended truce in place since 1997.

"All volunteers have been instructed to assist the development of purely political and democratic programs through exclusively peaceful means. Volunteers must not engage in any other activities whatsoever," the IRA command said in remarks addressed to the group's approximately 500 to 1,000 members.

The IRA killed about 1,800 people and maimed thousands more in hopes of forcing Northern Ireland out of the United Kingdom but never came close to achieving that goal. Its last major violence came during a 17-month stretch in the mid-1990s that included massive truck bombings in London, and Manchester, England. In all, some 3,650 people have died in more than three decades of sectarian violence.

The IRA statement said John de Chastelain, a retired Canadian general who since 1997 has been trying to persuade the IRA and other illegal groups to disarm, would be invited to decommission more hidden weapons bunkers soon. It said a Catholic priest and Protestant minister would be invited to witness the scrapping of weapons.

The IRA also appealed to Britain and Northern Ireland's Protestant majority to accept its new position as sufficient to renew negotiations on power-sharing, the core goal of the 1998 peace accord for this British territory.

Sinn Fein leader Gerry Adams said that as far as he was concerned, the IRA had declared its war over.

"There is a time to resist, to stand up and to confront the enemy by arms if necessary. In other words, unfortunately, there is a time for war," said Adams, who was a reputed senior IRA commander from the mid-1970s until May, when he reportedly stepped down from the seven-man IRA command. "There is also a time to engage, to reach out and put war behind us. This is that time."

The leaders of Britain and the Republic of Ireland warmly praised the IRA's announcement.

"I welcome the recognition that the only route to political change lies in exclusively peaceful and democratic means," Blair said at his office in London. "This is a step of unparalleled magnitude in the recent history of Northern Ireland."

Ahern, who has closely worked with Blair since 1997 to broker compromise in the British territory, said the statement heralded "the end of the IRA as a paramilitary organization."

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

White House spokesman Scott McClellan called the IRA pledge an "important and potentially historic" move toward peace.

He said the IRA's statement needs to be followed by actions that will demonstrate its commitment to giving up all paramilitary and criminal activities.

"We understand that many, especially victims and their families, will be skeptical," McClellan said. "They will want to be certain that this terrorism and criminality are indeed things of the past."

Sen. Edward Kennedy, D-Mass., said he hoped the IRA's statement "means we're finally nearing the end of this very long process to take guns and criminality out of politics in Northern Ireland once and for all."

Protestant leaders, deeply suspicious of IRA motives, stressed they would wait several months to test whether the IRA's words proved true. They noted the IRA was supposed to have disarmed fully by mid-2000 as part of the Good Friday accord, but did not start the process until late 2001 and stopped in 2003.

Ian Paisley, whose hard-line Democratic Unionist Party represents most Protestants, said IRA commanders "have failed to explicitly declare an end to their multimillion-pound criminal activity, and they have failed to provide the level of transparency that will be necessary to truly build confidence that the guns have gone in their entirety."

Security experts say the IRA retains much of its arsenal hidden in underground bunkers in the neighboring Republic of Ireland. The IRA received more than 130 tons of armaments from Libya in the mid-1980s, and police say the group continues to smuggle modern weaponry into the country.

All sides say they remain committed to resurrecting a joint Catholic-Protestant administration that would replace Britain as the primary government authority in Northern Ireland. But Protestants insist they won't work again with Sinn Fein, the IRA-linked party, until the IRA disappears as a threat to stability.

A four-party coalition led by Protestant and Catholic moderates gained power in 1999, but it fell apart in 2002 amid chronic arguments about IRA activities and arms.

Resurrecting power-sharing became more difficult in 2003 once voters — polarized by the diplomatic deadlock — shifted support to the opposite extremes of opinion: Adams on the Irish Catholic side and Paisley's Democratic Unionists on the British Protestant side.

A potential power-sharing pact between this unlikely couple fell apart in December when the IRA refused Protestant demands for disarmament to be recorded for public consumption. The IRA also rejected demands, chiefly leveled by the Irish government and Catholic moderates, for the IRA to renounce crime and accept the legitimacy of Northern Ireland's police force.

But then the Sinn Fein-IRA movement was thrown on the defensive by two events with exceptional repercussions — a mammoth robbery and an alcohol-fueled killing.

In December, police accused the IRA of robbing a Belfast bank of a world-record $50 million. The IRA denied involvement while restating its traditional position that its activities should never be described as "crime."

In January, IRA members knifed to death a Catholic civilian outside a Belfast bar, an action that highlighted the group's decades-old role as an intimidating power broker within its working-class Catholic bases. The IRA had killed others in similarly brutal circumstances in recent years, but this time the victim's family risked IRA retaliation by publicly campaigning for justice.

In March, President Bush greeted the victim's five sisters and fiancee on St. Patrick's Day, while Sinn Fein was barred from the White House for the first time in a decade.

The British, Irish and American governments united behind the position that power-sharing couldn't be restored unless the IRA fully disarmed and went out of business — disbanding in practice if not in name.