LONDON, England (AP) — It’s springtime in London, but, President Barack Obama might sense a chill in the air.

The US leader is being welcomed by British Prime Minister David Cameron and wined and dined by the royal family on a three-day visit to the UK that began late yesterday.

But Britain’s looming June 23 referendum about whether to stay in the 28-nation European Union (EU) has strained the “special relationship”, with several senior UK politicians bluntly telling the president to butt out of Britain’s debate. They have branded Obama “anti-British” and “unsuccessful” and accused him of meddling for suggesting that the US would be happier if Britain stayed in the bloc.

The White House says Obama is willing to speak out on the subject.

“If he’s asked his view as a friend, he will offer it,” US Deputy National Security Adviser Ben Rhodes said, adding that the American stance was clear. “As the president has said, we support a strong United Kingdom in the European Union.”

In an op-ed published in the

Telegraph newspaper, Obama wrote that Great Britain’s presence in the EU “magnifies” Britain’s influence and helps spread “British values”.

In the piece published yesterday evening as he arrived in London, Obama wrote that he’s offering his view “with the candour of a friend” and notes the decision will affect US interests.

Obama’s agenda before he leaves for Germany on Sunday includes talks with Cameron on the global economy, on countering an increasingly assertive Russia, and on the fight against the Islamic State group.

Peter Wittig, Germany’s ambassador to the US, told reporters yesterday he hopes Obama will use his influence with British politicians and society to try to persuade them to remain in the EU.

“I think that people will listen to him in the UK, and I am sure he will find the right words for that,” he said. “The UK looks to the US. It is a relationship with a long tradition and depth.”

The president’s British stopover — one of a series of international visits during his last year in office — will also include a lunch with Queen Elizabeth II at Windsor Castle today — a day after her 90th birthday — and a dinner hosted by Prince William, his wife Kate and Prince Harry at the younger royals’ Kensington Palace home.

But for the British media, the visit will be dominated by the debate over a possible EU exit, dubbed ‘Brexit’.

Cameron, who is meeting Obama for talks today at 10 Downing Street, is eager for the president’s intervention. Cameron is leading the campaign to stay in the EU, but faces opposition from within his own Conservative Government and widespread scepticism among voters about the benefits of membership in the bureaucratic Brussels-based behemoth that is the EU.

Obama’s former campaign manager, Jim Messina, is advising Cameron’s ‘Remain’ campaign, another sore point for backers of the ‘leave side’, who have lined up to accuse Obama of interfering.

Conservative lawmaker Jacob Rees-Mogg said Britons would not “want to be told what to do by a rather unsuccessful American president, who has had one of the least successful foreign policies in modern history”.

Nigel Farage, leader of the anti-immigrant UK Independence Party, called Obama “the most anti-British American president there has ever been.”