Northern Ireland Secretary James Brokenshire has warned of a snap election or a return to direct rule if Stormont parties fail to form a government by early May.
Mr Brokenshire issued the ultimatum as he confirmed the current round of talks to restore powersharing would be suspended for Easter.
"I believe that the outstanding issues between the parties are surmountable, but if no executive is formed by early May, I will need to take further steps to ensure Northern Ireland has the political stability it needs.
"This is likely to mean, however undesirable, either a second election or a return to decision making from Westminster."
A deal between the parties at Stormont has yet to be struck, almost six weeks after an Assembly election.
Party leaders say the talks have been constructive but there has been little progress on key points such as an Irish Language Act and legacy issues.
The Democratic Unionist Party (DUP) and Sinn Fein have blamed each other for the stalemate.
Parties had until Friday to resolve their differences, but that has been extended.
A date has yet to be set for the resumption of talks after the break.
The political deadlock came after a snap election on March 2 brought an end to Stormont's unionist majority and the DUP's lead over Sinn Fein was cut from 10 seats to one.
Sinn Fein and the DUP, whose agreement is a prerequisite of forming a new administration, are at loggerheads over a range of issues, each blaming the other for the impasse.
Mr Brokenshire said round-table talks would be suspended over Easter but bilateral meetings would continue.
"All the parties have been actively engaged and some further progress has been made, including on the formation of an executive and on legacy," he said.
"There is, however, still a lack of agreement between the parties on a small but significant number of issues.
"The restoration of devolved government remains achievable, but more time and a more focused engagement on the critical issues are required.
"The parties will have a final opportunity after Easter to reach agreement, building on the discussions which have taken place over the past six weeks."
He confirmed he would commence legislative steps at Westminster to stabilise the finances of the rudderless administration, by passing a law to enable the circulation of rates bills that pay for local council services.
He said he would also amend legislation to allow an executive to be formed in early May if a deal materialises.
If no consensus is reached, he said the Government would either call another snap election or suspend devolution and reinstate direct rule from London.
"On 2 March the people of Northern Ireland voted clearly for devolved government," he said.
"The parties mandated by that election still have a duty to provide the government for which they campaigned."