LONDON, March 12 (Reuters) - British Prime Minister Rishi Sunak will invite U.S. President Joe Biden to Northern Ireland in April to help celebrate the 25th anniversary of the Good Friday Agreement, which largely brought an end to three decades of political violence.

Sunak said on Sunday that he would issue a formal invite to the celebrations, which are due to take place in the middle of April.

"I'll be keen to invite him to come," he told reporters on his plane as he flew to the United States for meetings with Biden and Anthony Albanese, the prime minister of Australia. "It's not confirmed yet. But it will be something that obviously I'll be talking to him about.

"We've got this very important milestone to commemorate and celebrate - the 25th anniversary."

The Good Friday Agreement was a peace deal that largely ended the "Troubles", three decades of violence that had convulsed Northern Ireland since the late 1960s. It was signed on April 10, 1998, and partially brokered by the U.S. government of then President Bill Clinton.

The anniversary had been overshadowed in recent months after Northern Ireland's largest unionist party boycotted the power-sharing assembly that made up part of the peace deal, in protest at post-Brexit trade rules that treated the province differently to the rest of the United Kingdom.

Sunak has recently struck a new deal with the European Union to ease the checks and paperwork needed to move goods from Britain to Northern Ireland, but the Democratic Unionist Party is yet to say whether they will support the plan.

"What I'm concentrating on now is talking to everyone in Northern Ireland so we can find a positive way to move forward and get power-sharing up and running - that's my priority," Sunak said.