Irish state documents, released under the 30-year rule, revealed that President Jimmy Carter urged US speaker Tip O’Neill to lift a ban on arms sales to the RUC, the police force in Northern Ireland, at the request of British Prime Minister Margaret Thatcher.

The ban had been imposed after Irish American pressure because the RUC was seen as sectarian and blatantly one-sided.

Speaker O'Neill refused and said any arms deals from the US to the RUC would benefit the IRA whose supporters would be outraged by the American move.

"Immediately after her (Thatcher's) visit the president made a private plea to speaker O'Neill to change his position in regard to the arms sales," revealed the government papers.

"The British were, he said, among the best US supporters in dealing with terrorists who were holding US hostages in Iran and it seemed reasonable to expect similar support in their efforts to deal with terrorism in Northern Ireland."

The British government had ordered 3,000 .375 Magnum handguns and 500 .223 semi automatic rifles from the Sturm Ruger Corporation of Connecticut.

Thatcher went to Washington on December 17, 1979 to push for the ban to be lifted.

“She said she had made it perfectly clear, that, if that order were rejected it would not only be wrong, but a propaganda victory for the IRA,” the document stated.

Tip O’Neill then met Lord Carrington, the British Foreign Minister, on May 6, 1980, and told him his ban had been severely misinterpreted.

He said he would not allow a licence for arms trade “because such action could only benefit the Provisional IRA who would use the affair to collect more money and to try and gain support from politicians running for election in Irish-American districts”.

Irish officials looked at this overall discussion as the moment when the Northern Ireland issue took on an international dimension.

"The fact that an Anglo-American summit communique referred at all to Northern Ireland is a remarkable departure which represents a significant internationalization of the issue," the Foreign Affairs documents showed.