UK PM May faces double trouble

British Prime Minister Theresa May faces a fight on two fronts this week, battling to convince her own ministers and then Brussels as the Brexit talks come to a crunch.

She must see off the threat of a cabinet mutiny and then try to overcome the divorce negotiations logjam at a summit in Brussels -- though a breakthrough still seems elusive.

Time is running out on Britain's EU exit talks -- meaning this week's gathering of European Union leaders could prove decisive in striking a deal between London and Brussels.

With Britain set to leave the bloc at the end of March, European Commission head Jean-Claude Juncker is demanding "substantial progress" this week, specifically on the vexed issue of the UK's border with the Republic of Ireland.

EU President Donald Tusk has described the summit starting Wednesday as a "moment of truth" in the Brexit talks.

The hard work starts for May on Tuesday when she will rake over the Irish border issue with her cabinet, amid speculation that further ministers could quit if the PM ploughs on with her proposals.

Some diplomats in Brussels have suggested the leaders could talk through the night on Wednesday and approve the outlines of an agreement while they are still in the Belgian capital for broader talks on Thursday.