U.K. Trade Secretary Liam Fox, a veteran Brexit campaigner, told his colleagues to back Theresa May’s divorce deal or risk trapping the country in the European Union.

Speaking in a Bloomberg interview, Fox said there is still a majority in Parliament in favor of staying in the bloc and pro-Brexit members of Parliament who plan to reject May’s deal could thwart the whole process.

“There is still a remain majority in the House of Commons,” said Fox in the interview. “My biggest worry is we would be locked into some kind of customs union arrangement by Parliament.”

The prime minister also told broadcasters on Friday that the opposition Labour Party is trying to “frustrate” Brexit, but the argument may have more clout coming from Fox, who has been enlisted to bring around fellow Brexit-backers who loathe her deal because it maintains close links to the bloc.

Parliament looks set to vote against May’s accord on Dec. 11 and Fox wouldn’t be drawn on what should happen next. The Cabinet “as a whole” would decide, he said. Members of Parliament are working on tactics to either to send May back to the negotiating table to get a deal with even closer EU ties or engineer a second referendum. A general election is also a possibility.

“There clearly are a number of options,” he said.

Fox, whose job is to reach out around the world to forge new trade links with fast-growing economies, also struck a pragmatic note about the importance of EU commerce, which Brexiteers tend to downplay because they say growth lies beyond Europe.

In what appeared to be a warning to hardliners of the perils of a no-deal outcome, Fox said the U.K. couldn’t tilt too far away from Europe without “damaging our economic prospects.”