(CNN) -- Leaders from Britain, Ireland and Northern Ireland appeared together Friday to hail an agreement that saves the province's power-sharing government.
The leader of the Democratic Unionist Party (DUP) called it a "good day" for the province, and British Prime Minister Gordon Brown said it opened a "new chapter" for Northern Ireland.
"Let it be said in times to come that after decades of violence, years of talks, weeks of stalemate, this is the day we secured the future, a lasting peace, power being where it should be -- in the hands of the people of Northern Ireland, the strongest answer to those who would bring violence back to our streets," Brown said.
U.S. Secretary of State Hillary Clinton also praised the accord, calling it "another important step toward a full and lasting peace." The United States is prepared to help "build upon their efforts by promoting a new spirit of cooperation among all parties," she told reporters.
Video: N. Ireland's step toward peace
Sinn Fein and the DUP, the two largest political parties in the province, have been in a bitter political standoff for months over police powers and how to devolve them, or bring them under local control.
They held 10 days of talks before reaching an agreement Thursday.
Brown and Irish Prime Minister Brian Cowen flew in last week for emergency talks with the parties when it seemed the negotiations might fail. Had no agreement been reached, it could have brought the collapse of the Northern Ireland Assembly -- the legislature -- and forced new elections.
Because the power-sharing deal set up by the Good Friday Agreement in 1998 is fragile, there were fears that new elections might imperil the peace process.
"People across Northern Ireland feared that if the political process failed, they stood to lose all that had been achieved over these last few years," Brown said. "But what we have found in our talks is that, while the purpose of the discussions was an agreement on police and justice, what has emerged is more than that -- a new spirit of cooperation and mutual respect."
Brown said the devolution of policing and justice powers will happen April 12.
In addition, the British government has agreed to finance that devolution by making 800 million pounds ($1.26 billion) available, Brown said.
Earlier, Sinn Fein party leader Gerry Adams called the deal a "wonderful chance" for Northern Ireland to move forward.
"Today presents us, I think, with another new beginning," he told reporters.
The pro-Irish Sinn Fein has favored devolution, and Adams said it always seemed "a bit ridiculous" that the Assembly was not allowed to legislate on issues affecting its own people. The agreement reached Thursday with the pro-British DUP will help Northern Ireland take "more and more possession of our own affairs," he said.
"There will be begrudgers, but those that have been driving this need to go forward and forget about what happened for the last year or so, and see this as a genuine 'an tus nua,' a new beginning," Adams said, using Gaelic.
DUP leader Peter Robinson also said the agreement secures a positive future for Northern Ireland.
"No future generation would forgive us for squandering the peace that has been so long fought for," Robinson said. "No sane person wants to go back to the carnage, instability, violence ... that we have endured over recent generations."
