The European Union should immediately enter talks on its future relations with the United Kingdom in the event that British lawmakers pass a draft deal on the UK's exit from the bloc, the head of the EU's executive has said.

"If lawmakers in the House of Commons approve the withdrawal agreement in mid-January, we should begin work the very next day on the future relations between the UK and the EU," European Commission President Jean-Claude Juncker told Germany's Welt am Sonntag newspaper.

Following more than a year and a half of difficult negotiations, the UK Parliament is set to vote on the withdrawal agreement sometime after January 14. Prime Minister Theresa May delayed the vote in early December amid widespread opposition from both pro- and anti-EU lawmakers toward the agreement.

Many businesses have warned against the UK crashing out of the EU without a deal, an outcome that threatens to cause severe economic damage to the UK and the remaining 27 EU member states.

Juncker: UK will leave

UK Trade Secretary Liam Fox warned on Sunday that the UK's departure, which is scheduled for March 29, could be canceled outright if Parliament rejected May's draft deal.

"If we were not to vote for that, I'm not sure I would give [Brexit] much more than 50-50," Fox told British newspaper The Sunday Times.

But Juncker has said he believed the UK would leave the bloc despite calls from some UK lawmakers for a referendum over any final exit deal.

"That is what the people of the United Kingdom have decided," he said, referring to the June 2016 referendum in which 52 percent of voters approved of Britain leaving the EU.

Juncker also rejected claims the EU has been trying to keep the UK in the bloc.

"That is not our intention," he said. "All we want is clarity about our future relations. And we respect the result of the referendum."