US vice-president Joe Biden last night called on Northern Irish leaders to "keep going" in their pursuit of a deal to resolve the deadlock over flags, parades and the past.

At a dinner here attended by first minister Peter Robinson and deputy first Minister Martin McGuinness, Mr Biden said it was the responsibility of all sides to complete the work of the Good Friday accord.

"No-one is talking about forgetting the past, what we're talking about is coming to grips with the past and moving beyond it," he said after receiving the peace award of the American Ireland Fund.

Also present at the event, which raised $1 million (€721,462) for the fund, were Taoiseach Enda Kenny and Northern Ireland secretary Theresa Villiers.

Mr Biden's remarks are seen to reflect a sense of frustration in the Obama administration at the failure of talks chaired by US diplomat Richard Haas late last year.

They stand as a clear signal to Northern leaders that they should seek to regain the initiative.

Mr Biden said good substantive proposals had emerged from the Haas talks and suggested these could provide the basis for progress.

“So we encourage Northern Ireland’s political parties to try and keep going. Let’s remind ourselves of the basic promise of the Good Friday Agreement that we would give our children on both a chance to forge a shared history.”

Noting that other societies had found ways to deal with the past, he said Northern Ireland could too.

Recalling a speech he made eight years ago, Mr Biden said it remained the case that Northern leaders should move further make real the promises of the Good Friday deal.

“The people of Northern Ireland have been suffering for too long, and, if the truth told, are still suffering. There remains too much fear and mistrust and missed opportunity. Too many people on both sides are denied their dignity,” he said.

“It’s time as I said then to follow what President Lincoln once called the better angels of your nature because eight years later there remain signs that are not encouraging,” he added.

“In many places sectarianism has deepened and hardened, last year alone 700 policemen were injured in attempting to keep sectarian peace.

“It’s not enough to have a peace agreement written on paper. It must ultimately be written on the hearts of the people of Northern Ireland.”

Citing James Joyce, he said "history is still a nightmare from which they are constantly trying to awake" for too many people in the North.

“We shouldn’t forget how far we’ve come and what a different place Northern Ireland would have been were it not for the physical, moral courage of Northern Irish leaders on both sides including first minister Robinson and deputy [first] minister McGuinness and many others who are with us here tonight.”