Barack Obama has warned that the UK must stay in the European Union to retain its influence on the global stage. In an interview with the BBC, the president, who referred to Britain as America’s “best partner,” said the UK’s membership of the EU gives him “much greater confidence about the strength of the transatlantic union.”
Obama lauded the European project as making the world “safer and more prosperous,” while congratulating Cameron for meeting NATO's 2 percent of GDP target for defence.
"We don't have a more important partner than Great Britain. For him to make that commitment when he has a budget agenda that is confined, a budget envelope that is confined, is significant," he said.
In June, US defence secretary Ashton Carter said would be a "great loss to the world" if Britain "disengaged" by cutting its defence spending, noting that the nation had historically "punched above its weight."
He said: “The European Union… is part of the cornerstone of the institutions built after World War Two that has made the world safer and more prosperous and we want to make sure the United Kingdom continues to have that influence.”
He added that Britain's strength derived from its "willingness to project power beyond its immediate self-interests to make this a more orderly, safer world".
In response, MEP Daniel Hannan, a Conservative eurosceptic, tweeted: “I accept that there may be some arguments for Britain staying in the EU. Humouring Barack Obama is not one of them.”
Ukip MEP Patrick O’Flynn was equally dismissive, saying: “We need to look to our own national interest first."
Obama struck a similar tone at the G7 summit in Germany in June, the president urging Britain not to abandon Europe. He told reporters: "I would note one of the great values of having the United Kingdom in the European Union is its strength and leadership on a whole host of global challenges. So we are looking forward to the United Kingdom staying part of the European Union."
In an attempt to placate members of his party's right flank, Cameron has promised to renegotiate Britain's relationship with the EU ahead of a referendum scheduled for 2017. The prime minister has repeatedly stated he wants Britain to remain part of the union, but only if it reforms its rules.
Also in the interview, Obama revealed the biggest frustration from his time in office was not being able to pass "common-sense gun safety laws... even in the face of repeated mass killings."
He said: "If you look at the number of Americans killed since 9/11 by terrorism, it's less than 100. If you look at the number that have been killed by gun violence, it's in the tens of thousands."
"For us not to be able to resolve that issue has been something that is distressing," he reflected.
Bailout Fallout: Greece After EU Deal
(01 of13)
Open Image ModalGreek Prime Minister Alexis Tsipras talks to the media at the end of an Eurozone Summit over the Greek debt crisis in Brussels on July 13, 2015. European Commission President Jean-Claude Juncker said there was no longer any risk of Greece crashing out of the euro after Athens agreed a bailout deal with eurozone partners. (credit:THIERRY CHARLIER/AFP/Getty Images)
(02 of13)
Open Image ModalA person passes through an arcade with shuttered shops in central Athens, Tuesday, July 14, 2015. The experts say Greece has largely failed in previous crackdowns on tax evasion, which has been rampant for generations. An estimated 10 billion euros in taxes never makes it into government coffers annually. (credit:AP Photo/Petros Giannakouris)
(03 of13)
Open Image ModalA volunteer of Church-run Galini charity's soup kitchen sets the table in central Athens on July 14, 2015. Greek Prime Minister Alexis Tsipras was holding meetings with his party, faced with the tough task of selling a new bailout deal that requires Athens to push through draconian reforms within two days. (credit:ANGELOS TZORTZINIS/AFP/Getty Images)
(04 of13)
Open Image ModalPeople wait outside the Church-run Galini charity's soup kitchen in central Athens on July 14, 2015. Greek Prime Minister Alexis Tsipras was on July 14 holding meetings with his party, faced with the tough task of selling a new bailout deal that requires Athens to push through draconian reforms within two days/ (credit:ANGELOS TZORTZINIS/AFP/Getty Images)
(05 of13)
Open Image ModalPeople queue outside the Church-run Galini charity's soup kitchen in central Athens on July 14, 2015. Greek Prime Minister Alexis Tsipras was on July 14 holding meetings with his party, faced with the tough task of selling a new bailout deal that requires Athens to push through draconian reforms within two days. (credit:ANGELOS TZORTZINIS/AFP/Getty Images)
(06 of13)
Open Image ModalA protester argues with police while holding a Greek flag on the stairs leading to the Greek Parliament in Athens on July 13, 2015, during an anti-EU demonstration calling for the dismissal of accords between Greece and its European creditors and further austerity measures. Eurozone leaders struck a deal July 13 on a bailout to prevent debt-stricken Greece from crashing out of the euro forcing Athens to push through draconian reforms in a matter of days. (credit:LOUISA GOULIAMAKI/AFP/Getty Images)
(07 of13)
Open Image ModalProtesters participate in an anti-EU demonstration in Athens on July 13, 2015, calling for the dismissal of accords between Greece and its European creditors and further austerity measures. (credit:LOUISA GOULIAMAKI/AFP/Getty Images)
(08 of13)
Open Image ModalPeople demonstrate in front of the stairs leading to the Greek parliament in Athens during an anti-EU demonstration in Athens calling for a 'NO' to any agreement with the creditors on July 13, 2015. (credit:LOUISA GOULIAMAKI/AFP/Getty Images)
(09 of13)
Open Image ModalLeftists protesters hold a banner in front of the Greek parliament in Athens, during an anti-EU demonstration calling for a 'No' to any agreement with the creditors, on July 13, 2015. (credit:ANDREAS SOLARO/AFP/Getty Images)
(10 of13)
Open Image ModalA man sits alone with his thoughts as protesters gather outside the Greek parliament to demonstrate against austerity after an agreement for a third bailout with eurozone leaders on July 13, 2015 in Athens, Greece. (credit:Christopher Furlong/Getty Images)
(11 of13)
Open Image ModalA woman wearing a hat in the colours of Greece's national flag, looks at wallets designed as Euro banknotes on display, outside a kiosk in central Athens, Tuesday, July 14, 2015. The eurozone's top official says it's not easy to find a way to get Greece a short-term cash infusion that will help it meet upcoming debt repayments. (credit:AP Photo/Petros Giannakouris)
(12 of13)
Open Image ModalButchers wait for clients in a meat market in central Athens, Tuesday, July 14, 2015. Greek Prime Minister Alexis Tsipras was seeking Tuesday to rally his party members to support a preliminary rescue deal struck with Greece's European creditors that includes measures so onerous some of his own ministers were in open revolt. (credit:AP Photo/Emilio Morenatti)
(13 of13)
Open Image ModalSenior citizens wait to collect their pensions outside a National Bank of Greece branch in Kotzia Square on July 13, 2015 in Athens, Greece. Eurozone leaders have reportedly made an 'agreement' on the Greek debt crisis in Brussels. After lengthy talks EU President Donald Tusk tweeted that a bailout programme was 'all ready to go'. (credit:Photo by Christopher Furlong/Getty Images)