US President Jimmy Carter urged one of the most powerful American politicians of his time to lift a ban on arms sales to the RUC.
Government papers released under the 30-year rule revealed Carter privately pleaded with US speaker Tip O'Neill to end the embargo at the request of British Prime Minister Margaret Thatcher.
O'Neill, a renowned Irish-American congressman, said arms deals would benefit the IRA whose supporters would stir up publicity for fundraising.
"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," the Foreign Affairs documents revealed.
"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."
British Ambassador to Washington Peter Jay, who met Tip O'Neill on June 5, 1979, said the ban created an "alleged imputation" that the RUC was a sectarian force and an instrument of repression of the Roman Catholic minority in the north.
The papers also revealed that President Carter was keen to allow the arms trade.
This point in relations with the US was regarded by Irish officials as the time when the Northern Ireland question 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 internationalisation of the issue," the Foreign Affairs papers showed.