BELFAST (Reuters) - The United States called on the Irish Republican Army on Wednesday to lay down its arms sooner rather than later so Northern Ireland can find permanent peace.

"I would very much hope that the IRA would respond soon," said Mitchell Reiss, President George W. Bush's special envoy, as Washington joined forces with London and Dublin to try to get home rule returned to Protestants and Catholics in the province.

Last month Sinn Fein's Gerry Adams appealed to the paramilitaries to use words, not guns to fulfil their aim of ending British rule in Northern Ireland.

Reiss, sandwiching a trip to Belfast between talks in London and Dublin, said: "Everyone I have spoken with so far recognises there is a need for the IRA to respond positively and everyone has said sooner is better than later."

"There is some concern that if it does continue to delay longer, at least much longer, the situation isn't going to remain the same," he warned.

But Reiss said it was important to be patient so that the IRA gave a positive and unambiguous answer.

His visit marks a renewed push to get Northern Ireland's feuding Catholics and Protestants back to the negotiating table after hardliners on both sides of the sectarian divide cemented their grip in this month's British election.

Both Adams and firebrand preacher Ian Paisley, who heads the Democratic Unionist Party (DUP), are meeting Prime Minister Tony Blair in London.

Paisley, who fervently wants to maintain ties with Britain, refuses to talk to Adams until the IRA renounces its campaign for a united Ireland by publicly surrendering its weapons.

Blair -- at the beginning of a third term in office that he has said will be his last -- is likely to make a last-ditch effort to restore self-government to the province in order to polish a legacy tarnished by the war in Iraq.

Peace has largely been restored to the province during his leadership following an IRA ceasefire but a lasting political solution has proved elusive.

An assembly set up under the 1998 Good Friday Peace Agreement to give both sides a say in Northern Ireland's affairs was short-lived, while a high profile murder outside a Belfast pub and a massive bank robbery blamed on the IRA have made the DUP more determined than ever not to negotiate with Sinn Fein.

Reiss made a particular point in Belfast of seeing the family of the murdered man, Robert McCartney.

They have taken their case to the White House and the European Parliament but still no one has been charged.

"We are a long way from home in terms of getting justice for Robert but I think so far it is going in the right direction," Reiss told reporters after meeting McCartney's sisters.