The Prime Minister has urged Northern Ireland's political leaders to restore powersharing as soon as possible.
Theresa May held separate telephone conversations with DUP leader Arlene Foster and her Sinn Fein counterpart in Northern Ireland, Michelle O'Neill.
Dialogue has intensified in recent weeks between the former coalition partners in devolved government, both parties have acknowledged.
A Downing Street spokeswoman said: "In separate phone calls the Prime Minister made clear the importance of restoring a powersharing Executive to Northern Ireland as soon as possible and she recognised their continued leadership towards reaching agreement.
"They discussed key outstanding issues that remain for both parties and the Prime Minister encouraged both leaders to come to an agreement soon in the interests of everyone in Northern Ireland.
"The Prime Minister assured them both that the Northern Ireland Secretary (James Brokenshire) would continue to work closely with the parties towards a successful outcome."
Mrs O'Neill has said more than nice words are necessary to restore the ministerial Executive at Stormont while the DUP has insisted it has no preconditions for returning to government and remains committed to powersharing.
Formal talks between the two largest parties in Northern Ireland have yet to resume following a break for summer.
Ministers have not sat at Stormont for months after the late Martin McGuinness resigned as deputy first minister in a row over the DUP's handling of a botched green energy scheme at the start of the year.
Since then a dispute over the status of the Irish language has been among the issues dividing the parties.
Mrs Foster has suggested that cross-community legislation could be introduced to protect the rights of Irish language and Ulster Scots speakers.
However, this was rejected by Sinn Fein, who said the proposal was "nothing new".
