LONDON (REUTERS) - Britain's foreign minister Boris Johnson said he was not going to resign, when questioned on Tuesday (Sept 19) following reports that he could quit before the weekend if his Brexit demands were not met by Prime Minister Theresa May.

May is due to make a speech on Brexit on Friday and the Daily Telegraph newspaper reported that close friends of Johnson believe he will have no choice but to walk away if she advocates permanently paying for access to the EU's single market.

Speaking in New York, Johnson was asked by reporters if he planned to resign in footage aired by Sky News.

"No... of course not, we're going to deliver a fantastic Brexit," he said.

"We're working together, and the key thing is to make sure Britain can take advantage of the opportunities that Brexit provides."

May later backed Johnson in an interview with Sky News.

"Boris is doing good work as Foreign Secretary," she said, according to a Tweet by Sky News reporter Beth Rigby.

May also said she was confident of getting her whole senior team of ministers to back her Brexit strategy, which she is due to lay out at a specially convened Cabinet meeting on Thursday before making her Brexit speech in Florence on Friday.