Theresa May has canceled a vote in the British Parliament on her Brexit deal in order to avoid a crushing defeat. The vote was due to take place Tuesday and would have almost certainly seen the deal that May thrashed out with EU leaders be overwhelmingly rejected. The vote will now be rescheduled as May continues to attempt to persuade lawmakers to back her deal by going back to the EU to ask for further concessions. The main criticism of the deal is that it would keep the U.K. aligned with EU customs rules until a future trade deal is agreed to prevent a physical border between Northern Ireland and the Republic of Ireland. Some lawmakers fear that would indefinitely tie the U.K. to the EU with no say over its rules. May said it is this issue which she will now urgently attempt to renegotiate. It's unclear when parliament will get to vote on the deal—any agreement requires the backing of parliament before it can become law. Earlier Monday, the top European court ruled the U.K. could cancel Brexit without having to get permission from the 27 other members of the bloc.