A senior member of the DUP's negotiating team has said doubts remain over whether an agreement can be reached to restore devolution at Stormont.
Jeffrey Donaldson has dampened optimism expressed by Minister for Foreign Affairs Simon Coveney, who said yesterday that the executive could hopefully be restored within weeks.
A row between Sinn Féin and the DUP over an eco-boiler scandal collapsed the power-sharing executive last January and there has been no executive in place since then.
A series of talks between the main parties aimed at restoring the devolved institutions at Stormont have so far been unsuccessful.
Northern Ireland Secretary of State James Brokenshire has previously indicated that if a resolution is not reached by mid-October, direct rule from London may be introduced.
Mr Donaldson told the Press Association that while progress was being made in the talks aimed at restoring the power-sharing institutions, a "question mark" still remains over whether a deal could be struck between the DUP and Sinn Féin.
When asked if he shared Mr Coveney's optimism, the he said: "We have been making progress in the talks and there has been a more meaningful engagement in the last couple of weeks between the parties, but there remain gaps between us."
He added: "We will continue to work at it. We absolutely want to see an executive up and running as soon as possible.
"But it is difficult to predict at this stage when we might get agreement and if we will get agreement - there remains a question mark.
"Progress is being made but that does not mean in the end there will be an agreement, but we are determined to do our best to get one."
For several months, one of Sinn Féin's main demands before returning to the executive was that DUP leader Arlene Foster step aside as First Minister until the conclusion of a public inquiry into the eco-boiler (Renewable Heat Incentive) scandal.
When asked if this was still a red line for Sinn Féin in the talks process, Mr Donaldson said: "I don't want to comment on the specifics of the negotiations, but we are pleased with progress that has been made, but there are still issues to be resolved."