WASHINGTON - David Cameron became "distracted" after the 2011 intervention in Libya, US President Barack Obama has said.
Speaking to the Atlantic magazine, he said the operation went as well as he had hoped, but Libya was now "a mess".
The article also said he had warned the PM the UK would have to pay its "fair share" and spend 2% of GDP on defence.
In response, Number 10 said there were "many difficult challenges" in Libya, while the White House said it deeply valued the UK's contributions.
Downing Street did not comment on President Obama's remark to the PM about defence spending, reportedly made before Chancellor George Osborne said the government would fulfil a Nato pledge to spend 2% of national income on defence last year.
In response to the interview, a spokesman for the US National Security Council said Mr Cameron had been "as close a partner as the president has had" adding that "we deeply value the UK's contributions on our shared national security and foreign policy objectives".