David Cameron pledged to "battle hard for Britain right through the night" as he braced for a showdown with EU counterparts over his renegotiation demands.
The Prime Minister insisted he was confident of getting a "good deal" despite other leaders queuing up to dismiss his call for a four-year ban on in-work benefits for migrants.
He admitted there would be no agreement at the two-day Brussels summit, as had originally been hoped. Instead he said the gathering needed to put "momentum" behind the negotiations.
Speaking to reporters as he arrived, Mr Cameron pointed out that the EU Referendum Bill had received royal assent and the UK's in-out vote would definitely take place by the end of 2017.
"Tonight here in Brussels, we are going to have a conversation dedicated to Britain's renegotiation of its position in Europe, and I want to see real progress on all the four areas I have mentioned," he said.
"We are not pushing for a deal but we are pushing for real momentum.
"I am going to be battling hard for Britain right through the night.
"I think we will be getting a good deal."