Northern Ireland's returning secretary of state has warned the latest deadline to restore devolution is "final and immovable".
James Brokenshire also made clear the reintroduction of direct rule from Westminster is on the cards if an agreement does not materialise by June 29.
"Northern Ireland's political leaders now have this chance to take control and restore effective power sharing government under the current assembly mandate," he said.
"If they do not, the power to make decisions passes to others. Their choice in the next three weeks will shape Northern Ireland's future."
Mr Brokenshire also insisted the Government remained committed to the principles of the Good Friday Agreement and to governing in the interests of all the people of the region.
His comments came after a variety of politicians expressed concern that the mooted parliamentary deal between the DUP and Conservatives would undermine the Government's obligation, under the Good Friday accord, to be impartial in its dealings with Northern Ireland.
Three deadlines to restore powersharing have fallen by the wayside amid an ongoing dispute between the DUP and Sinn Fein.
Talks will resume in Belfast on Monday, having taken a break for the general election campaign, with a June 29 deadline.
Mr Brokenshire said there would not be another extension.
He added: "It is a privilege to have been asked by the Prime Minister to continue to serve as Secretary of State for Northern Ireland - particularly at such a crucial moment for Northern Ireland and the whole United Kingdom," he said.
Honoured & humbled to have been re-elected as Conservative MP for Old Bexley & Sidcup & to continue to serve this great community #GE2017 pic.twitter.com/Dw3uW0g621— James Brokenshire (@JBrokenshire) June 9, 2017
"The UK Government remains steadfast in its commitment to the Belfast Agreement and to governing in the interests of all parts of the community in Northern Ireland. It provides the basis for Northern Ireland's continued political progress and as the Government we remain firmly committed to this.
"My immediate priority is reaching agreement on restoring an inclusive power-sharing Executive - which is what the people of Northern Ireland voted for in the March Assembly elections.
"The statutory deadline to restore a functioning Executive to Northern Ireland is 29 June. Time is short but there was real progress in the last round of political discussion. Agreement between the parties can be reached if there is goodwill on all sides.
"Talks must resume again as soon as possible and I will meet the party leaders and Irish Foreign Minister Flanagan in Belfast tomorrow. All those involved must engage in the full knowledge that the deadline of 29 June is final and immovable.
"The UK government will do everything in its power, working alongside the Irish government in relation to those areas where they have responsibility, to contribute to and support the process, steadfastly upholding the principles of the Belfast Agreement and its successors.
"Like the overwhelming majority across the community in Northern Ireland, I believe a devolved government in Belfast is the best way to address the key decisions which affect people's day to day lives - whether these relate to the economy, security, public services or issues of policing and justice, as well as addressing the legacy of the past.
"A Northern Ireland Executive also has a vital part to play in ensuring that Northern Ireland's interests are represented as the UK prepares to leave the EU."