The PM faces a showdown in Parliament later as MPs aim to take control of the agenda to stop a no-deal Brexit.
Ex-chancellor and Tory rebel Philip Hammond said he thought there was enough support for the bill, seeking to delay the UK’s exit date, to pass.
No 10 officials warned the prime minister would push for an election on 14 October if the government loses.
Boris Johnson said he did not want an election and progress with the EU would be “impossible” if MPs won.
Meanwhile, Jeremy Corbyn said the Labour Party was ready for a general election.
But shadow Northern Ireland secretary Tony Lloyd later said Labour would vote against any government plans to hold a general election before the UK is due to leave the EU on 31 October.