Donald Tusk said Germany's Angela Merkel had warned Johnson that a deal is now "overwhelmingly unlikely".

The host of next week's European summit, EU Council President Donald Tusk, on Tuesday accused Prime Minister Boris Johnson of trying to shift blame for the failure of Brexit talks.

"What's at stake is not winning some stupid blame game," Tusk declared, in a Twitter message addressed directly to the British leader.

"At stake is the future of Europe and the UK as well as the security and interests of our people. You don't want a deal, you don't want an extension, you don't want to revoke, quo vadis?" he said, using Latin for "where are you going?"

Tusk, whose council represents the leaders of EU member states, was reacting after Downing Street said Germany's Angela Merkel had warned Johnson that a deal is now "overwhelmingly unlikely".

Johnson's Brexit envoy, diplomat David Frost, is in Brussels for technical talks on a possible withdrawal agreement to put to EU leaders at next week's Brussels summit.

But the two sides are still far apart over future customs arrangements for Northern Ireland, and EU officials were forced to deny reports from London that talks are close to breaking down.

"From our side we reiterate that the EU position has not changed. We want a deal, we are working with the UK for a deal," spokeswoman Mina Andreeva told reporters.

"Technical talks are continuing today so I don't see how talks could have actually broken down if they are happening today and in the days to continue," she said.

Talks between Frost and junior EU officials were to begin later Tuesday, then chief EU negotiator Michel Barnier was to meet Irish foreign minister Simon Coveney in the evening.

On Wednesday, Barnier is to brief the European Commission and officials have said the talks must lead to a legal text by Friday if they are to be considered at the October 17-18 summit.