Over the weekend chancellor Philip Hammond said it is "physically impossible" for the UK to leave the EU on 29 March. Hammond said a "short extension" to Article 50 was necessary to enable the government to pass all the legislation required to enact Brexit.
MPs are due to vote on Theresa May's Brexit deal for a third time next week, after it failed to win over MPs in earlier attempts this year. In a series of votes last week, MPs voted to reject a no-deal Brexit in all circumstances and for an extension to Article 50.
"If the Prime Minister's deal is able to muster a majority this week and get through, then we will need a short extension," Hammond said. "It is physically impossible to leave on 29 March, but we would be able to leave very soon. A long extension would mean Britain could have no choice but to participate in the elections to the EU parliament.
Brexiters have been warned to back May's deal if they want to avoid a long extension to Article 50, which EU leaders have hinted is the only kind of extension they will entertain. Ministers have however warned that a long delay could jeopardise Brexit by creating a window for a general election or second referendum to take place.