President Obama, speaking to reporters in London Friday, defended his prior comments urging British voters to remain in the European Union, following scathing criticism that he was meddling in the U.S. ally's affairs.

“I don’t believe the E.U. moderates British influence in the world, it magnifies it,” Obama said at a press conference at 10 Downing Street, alongside British Prime Minister David Cameron.

In recent days Obama has provoked ire from some British lawmakers for getting involved in the “Brexit” debate – earning him the title of “most anti-British American president there has ever been.”

“I don’t believe the E.U. moderates British influence in the world, it magnifies it.”

- President Obama

“Brexit” refers to Britain’s possible exit from the European Union. Britain is set to have a referendum this summer on whether to remain in the 28-member bloc. If a majority votes to leave it, Britain will exit.

“The E.U. has helped to spread British values and practices across the continent,” Obama said, adding that “the single market brings extraordinary economic benefits to the United Kingdom.”

He cast a grim picture of the economic stakes, saying flatly that the U.S. would not rush to write a free trade deal with a newly independent Great Britain.

"Let me be clear, ultimately this is something that the British voters have to decide for themselves but ... part of being friends is to be honest and to let you know what I think," he said. "It affects our prospect as well. The United States wants a strong United Kingdom as a partner."

Obama spoke on the first day of a three-day visit to London, likely the last of this presidency. The visit comes two months before a June referendum on leaving the union.

Polls suggest it will be a close-fought race, with most phone surveys indicating a lead for the Remain campaign while some online polls put the Leave camp ahead.

Obama described the votes as potentially damaging to the British economy. He said the U.S. is focused on writing a massive trade agreement with the European Union and would not prioritize a bilateral agreement with the UK. Britain would have to get "in the back of the queue," he said.

As he landed Thursday night, the president laid out his arguments in an op-ed in a London newspaper, harkening back to the "special relationship" forged by wartime allies President Franklin Roosevelt and Prime Minister Winston Churchill. With that special status comes with leeway to interfere, Obama argued, writing that he was offering his thoughts with the "candor of a friend."

Obama's candor wasn't universally appreciated. In increasingly heated language, critics accused Obama of meddling in British business. London Mayor Boris Johnson, head of the Leave campaign, called Obama's advice "paradoxical, inconsistent, incoherent" and suggested Obama's background played a role.

Writing in The Sun newspaper, Johnson recounted a claim that a bust of former British Prime Minister Winston Churchill was removed from the Oval Office after Obama was elected and returned to the British Embassy. The White House has said that a different Churchill bust is still in a prominent place in the presidential residence.

Johnson wrote that some said removing one of the busts "was a symbol of the part-Kenyan president's ancestral dislike of the British Empire, of which Churchill had been such a fervent defender."

Obama's late father was from Kenya, a former British colony that gained independence in the 1960s.

Obama has remained a broadly popular figure in Britain. In June 2015, three-quarters of Britons told pollsters they had confidence in his judgment on world affairs, according to a Pew Research survey.

That goodwill hasn't kept Britons in breaking from U.S. at key moments. In 2013, as Obama leaned on Cameron to join in threatened airstrikes in Syria, the House of Commons rejected the idea.

There have been other recent signs of stress on the relationship. British officials bristle over Obama's recent comments in the Atlantic magazine, in which he said he regretted trusting Europeans to stabilize Libya after the 2011 death of strongman Muammar Qaddafi. He specifically said Cameron had become "distracted by a range of other things" while Libya devolved into chaos.

The Associated Press contributed to this report.