BRUSSELS (Reuters) – European Council President Donald Tusk said on Friday he had no mandate to reopen Brexit negotiations with Britain, while the head of the bloc’s executive, Jean-Claude Juncker, said he “admired” Prime Minister Theresa May.

Tusk and Juncker were speaking at a news conference after two days of talks at an EU summit that were dominated by the issue of Brexit and saw the other 27 national leaders of the bloc offer May only vague assurances over their tentative Brexit deal.

“I have no mandate to organize any further negotiations. We have to exclude any further opening of the withdrawal agreement,” Tusk said. “But of course, we are staying here in Brussels and I’m always at the PM’s disposal.”

Juncker, captured by cameras earlier on Friday during an apparently heated exchange with May, said: “We have to bring down the temperature” around Brexit talks.

“We decided yesterday that the second after the approval by the two parliaments, the British one and the EU one… we will start negotiations on the future relations,” Juncker said.