Negotiations between the U.K. and European Union over their future relationship broke up a day early on Thursday amid warnings that big differences still exist between the two sides.

Discussions will still resume in London as planned next week, according to a statement from the British government on Thursday.

“The negotiations have been comprehensive and useful,” the U.K. said in the statement. “But they have also underlined the significant differences that still remain between us on a number of important issues.”

Michel Barnier, the EU’s chief negotiator, said in a separate statement that “serious divergences remain.”

The two sides resumed face-to-face meetings this week for the first time in three months in an effort to thrash out a trade deal before Britain’s final split with the bloc at the year-end. Without an accord, Britain and the EU will default to trading on terms set by the World Trade Organization, meaning the return of tariffs and quotas.