PARIS: French President Emmanuel Macron and future head of the European Commission Ursula von der Leyen both congratulated Boris Johnson on becoming Britain's next prime minister, although a key Macron ally warned Johnson that the EU would not budge on Brexit.

“First of all, congratulations to Boris Johnson for being nominated as Prime Minister. I'm looking forward to having a good working relationship with him," von der Leyen told a joint news conference with Macron in Paris on Tuesday.

“We have challenging times ahead of us," she added. “We have a duty to deliver something which is good for people in Europe and the United Kingdom."

Her views were echoed by the French leader, who said he would speak to Johnson as soon as he is officially installed as prime minister.

“I'm looking forward to working with him as soon as possible, not only on Europeans' issues such as Brexit negotiations, but also international issues that we have to closely coordinate on everyday with Britain and Germany, such as Iran and other international security issues."

Boris Johnson was elected leader of the governing Conservative Party and Britain's next prime minister on Tuesday, tasked with following through on his “do or die" pledge to deliver Brexit in just over three months' time.

Nevertheless, French politician Nathalie Loiseau – who is a member of the European Parliament and Macron's former Europe minister – warned Johnson that the EU would not be changing its position over Brexit.

“As much as we all want the relations between the UK and the EU to be as close and constructive as possible, @BorisJohnson's election doesn't change a simple fact : we have a good deal and the EU will stand by it," wrote Loiseau on Twitter.

“The EU is not for turning," added Loiseau, in an echo of a famous “the lady's not for turning" phrase used by former British Prime Minister Margaret Thatcher to highlight how Thatcher would stick to her positions.

Copyright Reuters, 2019