TAOISEACH Enda Kenny told Gerry Adams to use his influence to resolve the political impasse in the North as Stormont leaders continue to negotiate around the issue of welfare reform.
Mr Kenny spoke briefly to the Sinn Féin president in Washington yesterday, urging him to focus on "sorting out" the ongoing crisis.
The informal encounter took place at a lunch in Capitol Buildings and was described as "blunt" by one source present.
Mr Adams was also present in the White House as the Taoiseach insisted that the Stormont Agreement must be maintained.
The Louth TD stood at the back of the room as US president Barack Obama noted the absence of the North's first minister Peter Robinson and deputy first minister Martin McGuinness.
He told guests that the pair had remained home on St Patrick's Day in order to resolve the political stalemate.
Tensions between the Taoiseach and Mr Adams heightened significantly this week as the pair clashed over Sinn Féin's knowledge of the IRA sex abuse scandal.
In Atlanta, Mr Kenny launched a blistering attack on Mr Adams, accusing him of having information on kangaroo courts and the use of safe houses by the IRA.
"What are safe houses for? Are safe houses for raping people? Are they for interrogations? Are they for kangaroo courts? Gerry Adams knows full well what they are for. He knows where they are. He knows the people that were involved in them. His first duty here is, if he says 'anybody with information should give it to the gardaí', then he should present himself and tell them what he knows," Mr Kenny said.
In response, Mr Adams said Mr Kenny's accusations were "opportunistic and demeaning" to the office of An Taoiseach.
Meanwhile, a source directly involved in the Stormont negotiations has said the decision by Sinn Féin to withdraw support for welfare reform measures caused "bewilderment".
The source endorsed claims by Tánaiste Joan Burton and Fianna Fáil leader Micheál Martin that the move is connected with the IRA sex abuse scandal.
Sinn Féin has strongly rejected the claims that the move was linked to the Paudie McGahon and Mairia Cahill cases, insisting that the DUP reneged on commitments it made on welfare.