UK sovereignty aimed at getting sceptical Tories, including Boris Johnson, to get behind his reform deal.

Mr Johnson - who is being touted as a possible leader of the out campaign - has met Mr Cameron at Downing Street.

"I'll be back," he told reporters as he left Number 10, adding: "No deal, as far as I know."

BBC assistant political editor Norman Smith said the London mayor, who is "pivotal" to Mr Cameron's plans, would keep the PM waiting until he had returned from the summit before announcing which camp he would support, although his "no deal" comment was not thought to be a reference to his own concerns about sovereignty.

'Finely balanced'

Sources close to Mr Johnson say his decision on whether to back remaining in or leaving the EU ishave to do so

17 March:

The next scheduled EU summit - Mr Cameron has another chance to get a deal here. There has also been talk of a special summit at the end of February

Thursday 23 June:

Still seen as the most likely date of a UK referendum if Mr Cameron gets a deal in February or March, but he has until the end of 2017 to hold one

UK and the EU: Better off out or in?

European Commission President Jean-Claude Juncker said he expected proposed benefit changes to be at the heart of debate this week.

Czech Europe minister Tomas Prouza told the BBC he expected benefit curbs would apply only to new applicants, and not affect the existing 34,000 migrants in the UK who were recipients.

And Slovakia's Europe minister, Ivan