'Brexit talks get tougher close to the end'

British Prime Minister Theresa May said the Brexit talks were going to get tough towards the very end of the negotiations as she battled to win assurances from the European Union to persuade lawmakers to back her deal.

"Negotiations like this are always tough, there are always difficult times and as you get close to the very end, then that can get even more difficult because you're absolutely sorting out the last details of something," May said.

British Prime Minister said European Commission President Jean-Claude Juncker had clarified during an animated conversation on Friday that he had not called her "nebulous".

May had earlier been filmed on an official video remonstrating with Juncker at an EU summit in Brussels where she appeared to be accusing him of labelling her nebulous, a term he used on Thursday to describe the debate around Brexit.

"I had a robust discussion with Jean-Claude Juncker," she told reporters. "I think that's the sort of discussion you're able to have when you have developed a working relationship and you work well together.

"And what came out of that was his clarity that he had been talking, when he used that particular phrase, ... about a general level of debate."