Former U.K. Prime Minister David Cameron said in an interview that he called Barack Obama to tell him he regretted how the Brexit referendum in 2016 turned out.

"I am sorry," Cameron said he told President Obama and European leaders in an interview Friday with The Times. Obama, 58, warned before the vote that a British exit from the European Union would put them in the "back of the queue" in trade talks.

Cameron also dished in the interview about why he thought he failed to convince the electorate to keep the nation in the European Union.

"I think in the end we ended up with very strong technical and economic arguments, and the opposition had a very powerful emotional argument," the former leader of the Conservative Party said about the vote. "I think the issue of immigration plus that emotional argument was a winning combination for them. The argument about control, it resonated with people, and when you asked them, 'Well, what is it we’re going to control?' It was this issue of immigration."

Cameron, 52, said the emotional argument for those who wanted to stay did not work because he tried to point out the European Union fostered "positive relations" between potentially hostile countries, and people responded by saying, "Cameron predicts World War Three."

He also revealed he believed the current Prime Minister Boris Johnson behaved "appallingly" during the leave campaign.

"I say in the book: Boris had never argued for leaving the EU, right?" he said, adding Johnson and fellow conservative politician, Michael Gove, started "trashing the government of which they were a part, effectively."

The former prime minister dismissed the current potential for a no-deal Brexit as "a bad outcome" and stated that the U.K. should not rule out another referendum "because we're stuck."

The interview comes as Cameron is seeking to promote his newest book For the Record, which is being released this month. The books tells the story about how he "transformed the U.K. economy while implementing a modern, compassionate agenda."

Cameron resigned in 2016 after losing the Brexit referendum.

"I think the country requires fresh leadership," he said. "I do not think it will be right for me to try to be the captain that steers our country to its next destination."

In May, Theresa May resigned as prime minister after she failed to secure an exit deal between the U.K. and the European Union. Johnson, 55, is seeking leverage with the European Union by threatening to leave without a deal, but lawmakers within and outside of his party have sought to avoid that fate.