The Irish Republican Army withdrew its agreement on a method for reducing weapons, rebuffing Britain's efforts to create more negotiating time to salvage Northern Ireland's Catholic-Protestant government.

In a statement Tuesday, the IRA didn't rule out eventual partial disarmament. But the outlawed group emphasized that recent British and Protestant demands were "totally unacceptable."

The move — and the arrest of three suspected IRA members in Colombia — undermined efforts to preserve the power-sharing government at the heart of Northern Ireland's 1998 peace accord. Protestants said both developments demonstrate that the IRA is not ready to renounce violence.

"Withdrawing from an agreement which took two years to arrive at, only five days after republicans declared it as historic, can only play into the hands of those skeptics who have always doubted their intentions," said Britain's Northern Ireland Secretary John Reid.

Colombia announced Monday that it had arrested three suspected IRA members over the weekend, saying the men had spent five weeks teaching guerrillas how to use explosives. It was the first time work between the IRA and rebels in the South American country had been uncovered.

Northern Ireland's four-party coalition faced likely collapse last weekend, the apparent deadline for divided lawmakers to elect a Protestant to the government's vacated top post. But Britain intervened by taking power from local hands for 24 hours, postponing the leadership vote for six weeks, then restored power Sunday.

The IRA said the major Protestant party, the Ulster Unionists, should have accepted their commitment to disarm as adequate. The Ulster Unionists' rejection, "compounded by the setting of preconditions, are totally unacceptable," the IRA said.

"The subsequent actions of the British government, including their failure to fulfill their commitments, is also totally unacceptable," the group continued. "The conditions therefore do not exist for progressing our proposition. We are withdrawing our proposal."

The IRA said Britain had violated the 1998 pact, a view supported only by the IRA-linked Sinn Fein party, junior Catholic members of the coalition.

As a result, the IRA said, its agreement announced last week with retired Canadian Gen. John de Chastelain, chairman of an independent disarmament commission, had been withdrawn.

De Chastelain and the IRA had said they had found a mutually acceptable way for the IRA to put weapons "beyond use." But they kept the method secret. Nor did they specify when the process would start, or what political conditions the IRA had placed on such a move.

Senior Ulster Unionists said the withdrawal demonstrated that the IRA offer had never been genuine.

"The fact that they have so hastily withdrawn the offer indicates no intention, at this stage, to make serious movement on decommissioning," said Jeffrey Donaldson, using the politicians' favored term for disarmament.

"Taken together with the arrests of three senior IRA members in Colombia, it indicates to us that the IRA is as wedded as ever to the theology of revolutionary terrorism," said Donaldson, Ulster Unionist leader David Trimble's main rival for the party leadership.

Sinn Fein chairman Mitchel McLaughlin said the party "remains wedded to the Good Friday Agreement."

"Do we go off in a huff? Do we go home? No — we go back to work," McLaughlin told a news conference.

Trimble has twice formed administrations that included Sinn Fein as part of deals that, to work, required a start to IRA disarmament in exchange. Trimble resigned as the administration's leader July 1 after a second deadline for IRA disarmament lapsed.

Most political analysts calculate that Trimble has too little support among Protestant lawmakers to be re-elected leader unless the IRA offers more than words on disarmament.

In February 2000, the last time that the IRA's refusal to disarm undermined Trimble's hold on Protestant opinion, the IRA offered vague commitments to the disarmament commission hours before Britain suspended local powers indefinitely. The IRA responded by immediately withdrawing those commitments, chiefly an explanation for "the context" in which the group would get rid of weapons.

That crisis ended with a new May 2000 agreement in which Britain pledged to continue its military cutbacks and plans for police reform, the IRA issued an unprecedented pledge to begin putting weapons "completely and verifiably beyond use," and Trimble persuaded a bare majority of Ulster Unionists to resume work with Sinn Fein.

The Associated Press contributed to this report.