David Cameron has been forced to scrap plans for a Cabinet meeting on Friday to endorse his renegotiation of Britain's relationship with the EU, after efforts to secure agreement from fellow leaders became mired in delays in Brussels.
It had been expected that the Prime Minister would seal a deal with the other 27 EU leaders around lunchtime, before returning to London for a special Cabinet meeting to approve the package and agree a date for the promised in/out referendum - widely expected on June 23.
The meeting would also have given the green light to Eurosceptic ministers like Iain Duncan Smith and Chris Grayling to go out and campaign for Britain to leave Europe, and put pressure on waverers like London mayor Boris Johnson and Justice Secretary Michael Gove to spell out where they stand.
But Mr Cameron faced tougher than expected resistance from a number of EU states on issues ranging from welfare payments for migrant workers to protections for non-eurozone states as the single currency zone integrates further.
A planned "English breakfast" meeting to finalise the deal was put back to brunch, then lunch, then teatime and dinner, and, as the day wore on, EU officials announced the 28 leaders would not return to the negotiating table until 8pm.
Acknowledging his plans had been delayed, Mr Cameron said in a message on Twitter: "Negotiations are continuing into this evening. A Cabinet meeting won't be possible tonight. One will be held if and when a deal is done."
A Downing Street source said Mr Cameron was likely to have one-on-one meetings with his Danish, Czech and Dutch counterparts before this evening's round-table session.