Northern Ireland Secretary of State James Brokenshire has said the current situation in Northern Ireland is grave and that the clock was ticking on an election.
The Conservative MP made a statement to the House of Commons on Tuesday lunchtime following the shock decision by Martin McGuinness to resign as deputy First Minister.
He urged the parties to work together to find a way around the impasse.
He said it was "unhelpful" to talk about the suspension of the devolved institutions.
"That is entirely premature and unhelpful," he said.
Mr Brokenshire told MPs: "Yesterday Martin McGuinness submitted his resignation as deputy First Minister of Northern Ireland.
"This also means First Minister Arlene Foster ceases to hold office, although she is able to carry out some limited functions.
"Under the terms of the Northern Ireland Act 1998, as amended by St Andrews act 2007, my position is clear.
"Should the offices of first and deputy first ministers not be filled within seven days of Mr McGuinness's resignation then it falls to me as secretary of state to set date for an Assembly election.
"While there is no fixed timetable in the legislation, for me to do this it needs to be in a reasonable period.
"In his resignation letter Mr McGuinness said in the available period Sinn Fein will not nominate to the position of deputy First Minister.
"I am very clear in the event of the offices not being filled I have an obligation to follow the legislation.
"As things stand therefore an early Assembly election looks highly likely.
"I should add that once an election has been held the rules state that the Assembly must meet again within one week with a further two week period to form an executive.
"Should things not be achieved as they currently stand then I am obliged to call another election.
"Members should be in no doubt the situation we face is very grave and the government treats it with the utmost seriousness."
He said both the British and Irish governments would continue to support the DUP and Sinn Fein.
"We do, however, have to be realistic. The clock is ticking," he added.
"If there is no resolution then an election is inevitable, despite the widely held view that this election will change nothing and threaten the continuity of the devolved institutions."
The minister said he would immediately return to Northern Ireland to "do whatever he can to find a way forward".
He went on: "We are currently in the longest period of unbroken devolved government since the 1960s.
"This political stability has been hard gained, and it should not be lightly thrown away. In the 14 months since the Fresh Start Agreement significant advances have been made in areas such as addressing paramilitarism, supporting shared and integrated education and putting the Executive’s finances on a sustainable footing.
"This summer’s parading season passed off peacefully, and the long running dispute in North Belfast resolved.
"We have also been working intensively to build the necessary consensus to bring forward the bodies to address the legacy of Northern Ireland’s past set out in the Stormont House Agreement.
"I am in no doubt that what Northern Ireland needs at this time is strong and stable devolved government.
"Northern Ireland deserves fair, accountable, stable and effective government.
"To continue implementing the Belfast Agreement and its successors.
"To strengthen the economy.
"To ensure that Northern Ireland responds to the challenges and opportunities presented by EU exit.
"To build a stronger, shared society in which there is respect for everyone.
"And to address the legacy of the past in a way that enables Northern Ireland to move forward.
"We must not put all of this at risk without every effort to resolve differences. We must continue to do all that we can to continue building a brighter, more secure Northern Ireland that works for everyone."
None of the major political parties is excited about the election that has been thrust upon them. After a series of polls the piggy banks are empty, and with a reduction in MLAs from 108 to 90, most parties will lose a greater or lesser number of seats.
The DUP deserves most of the blame for exposing the abused Northern Irish electorate to an unnecessary election, but Gerry Adams has played a major part in turning a problem into a crisis.
In his ten years as Deputy First Minister, Martin McGuinness served alongside three DUP First Ministers. With one his relationship was astonishingly good, with another it was generally reasonable, while with the third - Arlene Foster - it was frankly terrible.
The sudden resignation of Martin McGuinness - obviously a very sick man - as Deputy First Minister is, as befits a republican bound by a code of omerta, also a clear political act. It has little to do with good or bad governance. McGuinness brings down First Minister Arlene Foster (and arguably strengthens the ageing Gerry Adams as president of Sinn Fein).