BRUSSELS: The president of the European Commission Jean-Claude Juncker told Britain's Prime Minister Boris Johnson on Thursday that EU officials have no mandate to renegotiate the Brexit withdrawal agreement.

The pair spoke on the telephone for the first time since Johnson took power on a platform of taking Britain out of the EU on October 31 with or without a formal divorce accord.

"President Juncker listened to what Prime Minister Johnson had to say, reiterating the EU's position that the Withdrawal Agreement is the best and only agreement possible -- in line with the European Council guidelines," Juncker's spokeswoman said after the call.

Juncker also repeated the EU's offer to consider inclusion of any new demands from the UK into a non-binding political declaration that was negotiated to accompany the divorce deal.

EU negotiators would "analyse any ideas put forward by the United Kingdom, providing they are compatible with the Withdrawal Agreement," the former prime minister from Luxembourg told Johnson.

Juncker's spokeswoman said "the two exchanged mobile phone numbers and agreed to remain in touch."

"President Juncker reiterated that the Commission remains available over the coming weeks should the United Kingdom wish to hold talks and clarify its position in more detail," she said.