People in Northern Ireland can no longer tolerate unionists thinking they have a veto over change, Sinn Fein has said.

Party president Gerry Adams was speaking at a news conference after the Ulster Unionists passed a party motion on Saturday challenging republicans to demonstrate they have left violence behind them.

Unionist ministers will withdraw from the power-sharing executive at Stormont on 18 January if they feel the IRA has not effectively moved away from violence and the prime minister fails to suspend Sinn Fein from the assembly.

The Ulster Unionists have proposed to enter into talks with Sinn Fein, the government and the other Northern Ireland parties over the next three months before taking a decision.

Gerry Adams: 'Unionists cannot halt change'

But Mr Adams said the Ulster Unionist Party had signed up to a "wreckers' charter" and the government must not concede any more concessions to unionists by allowing them to halt the political process.

"Sinn Fein is totally committed to the Good Friday Agreement and the peace process," he said.

"Our efforts in the time ahead will be to see that Agreement implemented. Our preference is that the unionists join with us in that enterprise.

"However, if the unionists refuse to be part of that process then the two governments must proceed anyway.

"Today's victory for the no camp will not deter us and will not stop the process of change. That will only happen if we give up and we and we are not for giving up."

SDLP leader and Deputy First Minister Mark Durkan said the Ulster Unionists had adopted an anti-Agreement agenda which was jeopardising devolution.

He said: "We face very serious political difficulties as a result of this decision.

"It's a clear threat not just to one political institution under the agreement, but to several."

'Lack of confidence'

But Northern Ireland Secretary John Reid said the government was "well aware of the lack of confidence caused both by paramilitary activity and political instability".

Dr John Reid: 'Agreement needs support of all parties'

"By definition any agreement must have the support of both sides and we are well aware of the lack of confidence caused both by paramilitary activity and political instability," he said.

"All involved in this process must be able to have confidence that the Belfast Agreement will be implemented in full."

Peter Robinson, deputy leader of the Democratic Unionist Party, dismissed the proposals as a stunt.

He said: "It is only the fear of electoral defeat at the hands of the DUP that has prompted them into action.

"It's the same old stunt again attempting to make the people of Northern Ireland believe that they are getting tough."

'Party united'

Ulster Unionist leader David Trimble and anti-Agreement MP Jeffrey Donaldson amended their proposals to Saturday's meeting of the party's ruling council to form a single motion which was passed without a vote.

Speaking afterwards, both men said that, despite clear differences before the gathering, the party was now united behind the motion.

Mr Trimble said it was not a case of a win for either faction in the party that was for or against the Good Friday Agreement.

The motion that was passed unanimously today is good news for the party

Jeffrey Donaldson Lagan Valley MP

The party leader also refuted suggestions that policy was being driven by Mr Donaldson.

"The people that won today are the people of Northern Ireland," he said.

"Everybody's a winner and the only way we will have loss out of this is if the paramilitaries do not reform."

Mr Donaldson said the party's ruling council was the policy making body and denied he was driving policy from the back seat.

"The motion that was passed unanimously today is good news for the party and good news for the process," he said.

The 860-strong Ulster Unionist Council will meet again on 18 January to take its decision on whether to withdraw from Northern Ireland's political institutions.