MPs return from summer recess tomorrow and the Commons will this week debate a bill presented by Labour former minister Hilary Benn which requires the Government to either reach a deal with the EU, or gain Parliament's approval for a no-deal exit by October 19.
If the Government has not met one of these conditions by the deadline, it will be required to write to the European Union seeking an extension, until January 31, 2020.
Details of a Bill which aims to prevent the UK from leaving the EU without an agreement have been revealed.
Mr Benn said: "The purpose of the Bill is to ensure that the UK does not leave the European Union on the 31 October without an agreement, unless Parliament consents.
"The Bill gives the Government time either to reach a new agreement with the European Union at the European Council meeting next month or to seek Parliament's specific consent to leave the EU without a deal.
In a statement in Downing Street following an unscheduled Cabinet meeting today, Mr Johnson urged his MPs not to join Labour leader Jeremy Corbyn in backing a ‘pointless’ delay.
He urged Tory MPs not to support the bill amid speculation he could call an election if he loses the Commons showdown, saying: "I don't want an election, you don't want an election."
But he said he would not seek an extension to the Brexit deadline.
Mr Johnson had to contend with the noise of protesters at the gates of Downing Street as he delivered his statement.
He said MPs voting against the Government would "chop the legs" out from under the UK's negotiating position: "I say, to show our friends in Brussels that we are united in our purpose, MPs should vote with the Government against Corbyn's pointless delay.
"I want everybody to know there are no circumstances in which I will ask Brussels to delay. We are leaving on October 31, no ifs or buts."
The Prime Minister claimed the chances of a Brexit deal are rising and he was "encouraged by the progress we are making" with Brussels.