The UK and Irish governments must inject "leadership and energy" into last-ditch talks to restore powersharing in Northern Ireland, Sinn Fein has said.
Claiming the Democratic Unionists (DUP) were still standing in the way of a deal, Sinn Fein's John O'Dowd told the governments to ramp up their involvement in the stalled negotiations.
An impasse over republican demands for legislation to protect Irish language speakers is one of the main impasses. The DUP is willing to legislate, but only if Ulster Scots speakers are included in any Act - a condition Sinn Fein has rejected.
The parties have until 4pm on Thursday to nominate ministers to a new coalition executive or they face the prospect of some version of direct rule be imposed from Westminster or yet another snap Assembly election.
Emerging from the talks venue at Stormont Castle in Belfast, Mr O'Dowd questioned the merit of extending the deadline to facilitate further discussions.
"Timescale is not the issue," he said.
"It is a willingness by the participants in the talks to resolve the outstanding issues."
The Sinn Fein negotiator added: "There is clearly an onus on the governments to inject energy into these talks, to inject leadership into talks and ensure the outstanding issues are resolved in the time-scale we have left to us."
The DUP has told the republican party to stop indulging in "high-wire acts" and get down to the job of delivering for the people.
Ulster Unionist (UUP) leader Robin Swann said his party would not provide "cover" for the DUP if it signed up to an Irish Language Act.
Revealing that the DUP and Sinn Fein did not attend a scheduled round table meeting inside the castle on Wednesday afternoon, he also warned that his party should not be taken for granted.
He said there were many issues the UUP wanted to raise, including mechanisms for dealing with the legacy of the Troubles and pensions for conflict victims.
"Our party will not be taken for granted in these talks or the formation of any executive," he said.
Sinn Fein has hinted movement was possible on one precondition - its opposition to DUP leader Arlene Foster returning as Stormont first minister while a public inquiry into a botched green energy scheme is ongoing - if the DUP gave ground on other matters.
Mrs Foster was forced from office in January when Sinn Fein's then deputy first minister, the late Martin McGuinness, quit in protest at the DUP's handling of the Renewable Heat Incentive (RHI) - a scheme that left the administration facing a £490 million overspend.
His move triggered a snap assembly election in March.
A number of attempts to restore powersharing between the five main parties following that poll floundered, with three UK Government deadlines for a deal having already been missed.