Theresa May is due at a summit in Brussels, hours after Conservative rebels in the Commons defeated the government in a key Brexit vote.
One rebel, Stephen Hammond, was sacked by the prime minister as a party vice chairman in the aftermath of the vote.
Other EU member states could decide to move forward to trade talks with the UK at their two-day summit.
Mrs May lost by just four votes, as MPs backed an amendment to the EU Withdrawal Bill by 309 to 305 - her first Commons defeat as prime minister.
Labour leader Jeremy Corbyn said it was a "humiliating loss of authority" for the prime minister.