Jean-Claude Juncker has raised the prospect of an emergency summit of EU leaders next week to decide on a Brexit delay, blaming ongoing chaos in Theresa May’s cabinet.

The European commission president said a letter from May requesting an extension to article 50, delaying the UK’s exit beyond 29 March, had not arrived overnight as expected.

The 27 EU heads of state and government had expected to discuss the terms of request and come to a unanimous agreement on their response at a summit starting on Thursday in Brussels.

But after a stormy cabinet meeting on Tuesday, a letter from Downing Street was not received by Donald Tusk, the president of the European council, who convenes the leaders’ summits.

Juncker said it appeared the British cabinet could not agree on the content of the correspondence. “My impression is ... that this week at the European council there will be no decision, but that we will probably have to meet again next week, because Mrs May doesn’t have agreement to anything, either in her cabinet or in parliament. As long as we don’t know what Britain could say yes to, we can’t reach a decision,” he said.

A senior EU official said: “At this stage we have not received an – already famous in the press – letter to President Tusk and we have not received the request from the UK for the extension of the period under article 50 in any other form.

“The situation, as it stands at this moment, is that there is no request from the UK for the extension for the negotiations under article 50. Maybe it will come, maybe it will not come.”

The official added that it was hoped the prime minister would still address the EU’s leaders on Thursday afternoon and “sketch out her plans and assessment of the situation in the UK”.

“And then there will be a debate among the 27”, he said. “I guess here again we have to demonstrate patience, which we have been demonstrating consistently during the process of the negotiations.”

The official refused to comment on whether the EU could offer a “short, super short, super long” delay. “To speculate about that we would at least need a request from the UK on the table,” he said. “As things stand, now I can say the EU27 leaders will have a discussion about Brexit state of play … This discussion will also include no-deal preparations.”

Juncker told Germany’s Deutschlandfunk radio station that “in all probability” Britain would not leave on 29 March but an extension “would have to produce, as an end result, an agreement from the British parliament to the [agreement] text which is before them”.

“If that doesn’t happen, and if Great Britain does not leave at the end of March, then we are, I am sorry to say, in the hands of God,” Juncker said. “And I think even God sometimes reaches a limit to his patience”.

The commission president reiterated the EU line that the withdrawal agreement will not be reopened under any circumstances.

He said: “There will be no renegotiations, no new negotiations and no additional assurances on top of the additional assurances we have already given. We will keep talking to the British. We are not in a state of war with Britain, we are in a state of negotiations, but the negotiations are concluded.”