President Barack Obama has said that a trade deal between the US and the UK could take almost a decade to negotiate if Britain votes to leave the European Union.
"It could be five years from now, 10 years from now before we're actually able to get something done," Obama told the BBC in an interview on Sunday.
Obama’s remarks came as Britons are preparing to vote on June 23 to decide on their country’s future in the European Union.
The US president, who is in the last nine months of his presidential term, arrived in London on April 21 to tell Britons that issues such as terrorism, migration and economic slowdowns could be tackled more successfully with the UK in the EU.
He told the BBC that Britain would not be treated preferentially over the EU when it came to negotiating a new trade deal.
"The UK would not be able negotiate something with the United States faster than the EU," Obama said. "We wouldn't abandon our efforts to negotiate a trade deal with our largest trading partner, the European market."
In an article published by the UK’s Daily Telegraph newspaper, Obama said UK’s EU membership had magnified Britain's place in the world and made the European bloc stronger and more outward looking.
Also, during a joint press conference with British Prime Minister David Cameron on Friday, the US president said the “special relationship” between the two countries makes the Brexit “a matter of deep interest to the United States.”
Obama’s comments infuriated anti-EU campaigners who accused him of interfering in UK internal politics.
London mayor and cabinet member Boris Johnson, who is also one of Britain’s most famous politicians, wrote in an article that Obama's arguments were "incoherent," "inconsistent" and "downright hypocritical."