BRUSSELS — With Britain and the European Union’s carefully crafted divorce deal headed for likely failure in the British Parliament this week, European leaders are bracing for more Brexit chaos – and warning they have little to sweeten the bargain for London.

The landmark 585-page agreement, a thicket of legalese that extracts Britain from the European Union after more than four decades of membership, has proved politically toxic in Westminster. Everyone from hardcore Brexiteers to pro-EU Brits finds aspects to dislike. But both British Prime Minister Theresa May and EU leaders warn that the deal is the best on offer, given the red lines on both sides of the negotiating table.

Europeans have gone slackjawed at London’s political chaos, with normally demure diplomats comparing the process there to a slow-motion car wreck. They say they can offer little other than cosmetic tweaks that might help May save face with her own Conservative Party. And they have begun to accelerate their emergency planning to prepare safety nets that could avoid some of the humanitarian and economic chaos that might happen if Britain crashes out of the European Union on its deadline of March 29 with no other plan in place.

“It’s taken many people time to understand that things really are as bad as they are in the U.K.,” said Lotta Nymann-Lindegren, a former Finnish diplomat who focused on Brexit issues and now works at the Miltton consultancy. “It’s been a real eye-opener that an issue like this can cause such domestic political chaos.”

Although May could still pull off an upset victory, discussions in both London and Brussels revolve around the expected margin of her defeat on Tuesday.