'Brexit' is not going to happen, says EU's Juncker

European Commission chief Jean-Claude Juncker insisted Wednesday that Britain would not leave the EU, as leaders prepare to discuss David Cameron's reform demands at a summit next month.

"'Brexit' is not going to happen -- 'Brexit' is not going to happen," Juncker emphatically repeated during a public event in Brussels when asked about negotiations on Britain's place in the 28-nation bloc.

"I have just spent three years avoiding Grexit, I am not going to spend three years of my life facilitating Brexit," added Juncker, who played a key role in keeping debt-stricken Greece in the eurozone.

"I want a fair deal with Britain."

Juncker's comments come despite a warning from European Council president Donald Tusk last week that it would be "very, very tough" to reach a deal by December's EU summit.

In a major speech earlier this month outlining Britain's demands for change following pressure from EU leaders, Cameron warned he was ready to "think again" about British membership if he could not strike a deal.

Among proposals he laid out are: improved competitiveness, greater "fairness" between eurozone and non-eurozone nations and sovereignty issues including an exemption from the aspiration of ever-closer union.

Most controversial is the demand to ban EU migrants to Britain from claiming certain state benefits for four years after arriving.

Cameron will put whatever deal he gets to the British people in an in-out referendum before the end of 2017.