BRUSSELS: European Union leaders are set to open the next phase of Brexit talks at a summit this week, but may toughen their conditions after Britain cast doubt on whether a deal on divorce terms is binding, reports AFP.

British premier Theresa May and European Commission chief Jean-Claude Juncker reached a last-minute agreement Friday regarding the Irish border, Britain’s divorce bill and the rights of EU migrants.

The leaders of the 27 remaining countries are to decide on Friday whether to approve that deal and green light the opening of talks on a post-Brexit transition period and the bloc’s future relationship with Britain.

But they have been alarmed by comments by Britain’s Brexit Minister David Davis in which he said that Britain would not pay the bill without a trade agreement, and that Friday’s deal was a “statement of intent” rather than “legally enforceable.”

European Parliament Brexit coordinator Guy Verhofstadt said Davis’s comments were “unacceptable” and a self-inflicted “own goal” for Britain as the EU would now take a tougher stance. “I have seen a hardening of the position of the council (of EU leaders) and hardening position of the parliament,” Verhofstadt told reporters at the parliament in Strasbourg, France on Tuesday.

The European Parliament is set to back in a vote on Wednesday the opening of the second phase of Brexit talks. MEPs will also have a final say on any Brexit deal in 2019.

With the possibility of a British backtrack in mind, the EU negotiating guidelines that leaders are set to adopt on Friday will say phase two talks can only start once the divorce commitments are “translated faithfully in legal terms.”

The EU leaders will also say that talks on trade will not start until March, to give the British government time to provide “further clarity” on what it wants from the future relationship. Britain has said it will leave the EU’s single market and customs union but has given no hint of a wider plan, with May’s cabinet only having its first meeting on the subject next week—a full year and a half after the June 2016 Brexit referendum.