U.S. President Donald Trump has endorsed Boris Johnson to replace Theresa May as British prime minister | Tolga Akmen/AFP via Getty Images Trump backs Johnson, takes pop at Macron ahead of European trip US president says frontrunner to be next British PM is ‘very talented.’

Days ahead of a visit to the United Kingdom and France, Donald Trump is already breaching protocol, supporting Boris Johnson to be the next British prime minister, and taking a dig at Emmanuel Macron.

"I think Boris would do a very good job. I think he would be excellent... I think he is a very good guy, a very talented person," Trump said in an interview with The Sun.

The U.S. president stopped just short of a formal endorsement of Johnson but boasted his backing could have a big impact in the race to succeed Theresa May and Conservative party leader and prime minister.

"I could help anybody if I endorse them," Trump said adding that others among the 12 candidates "have asked me for an endorsement too."

Johnson is seen as the frontrunner to become next Tory leader. But Trump also spoke favourably of another contender, Foreign Secretary Jeremy Hunt, praising his proposal to significantly increase U.K. defense spending.

"I think that's great. I love it," Trump said.

The U.S. president also criticized May's negotiating tactics with the European Union over Brexit.

"I think that the U.K. allowed the European Union to have all the cards, and it is very hard to play well when one side has all the advantage," Trump said.

Trump is expected in the U.K. on Monday for a three-day state visit that will include talks with May on issues including their differences over how to handle Iran and Chinese telecoms giant Huawei. Queen Elizabeth is also hosting a banquet in his honor.

Trump will then go to France to continue D-Day commemorations and hold talks with Macron, during which the two will discuss their divergent positions on Iran and trade negotiations.

Macron recently objected to trade talks between the EU and U.S. on environmental policy grounds, citing Trump's withdrawal from the Paris climate agreement.

But Trump claimed the Yellow Jackets protest movement that erupted in France late last year over a carbon tax showed he had made the right call on the climate pact.

"I think [the] Paris [climate agreement] has turned out to be something that I made absolutely the right decision. Look at what's going on in Paris," Trump said,

Last time Trump was in France to commemorate Remembrance Day in November, he also used the Yellow Jackets movement to criticize Macron. France and the U.S. have been increasingly at odds since Trump took office, clashing over trade, Iran, climate and Macron's calls for a European military.