President Obama hailed the potential for a "ground-breaking" free-trade deal between the European Union and the United States on Monday, at the start of the G8 summit in Northern Ireland.
"The US-EU relationship is the largest in the world, it makes up nearly half of global GDP," he said. "America and Europe have done extraordinary things before. This transatlantic trade and investment partnership is going to be a priority."
David Cameron, who is hosting world leaders in Northern Ireland, said the trade deal was a "once in a generation prize" that could lead to the creation of two million jobs.
The prime minister, appearing on stage without a suit jacket or tie and with his shirtsleeves rolled up, said it was the biggest bilateral trade agreement in history and would have "a greater impact than all a the other trade deals put together".
Speaking alongside Cameron as well as the president of the European Commission, José Manuel, and Herman Van Rompuy, the president of the European Council, Obama also announced the first round of EU-US trade talks to take place in Washington next month.
However the deal is one of the official items on the G8 agenda that threatens to be overshadowed by the on-going bloody civil war in Syria.
Cameron held private talks earlier today with Obama - who has said he may send weapons to opposition forces seeking to oust Syria's Bashar Assad - before the US president meets his Russian counterpart Vladimir Putin, Assad's most powerful international backer.
The dramatic gulf between Russia and the West over Syria was laid bare in talks between Cameron and Putin at Downing Street yesterday, when the Russian president warned the international community to be wary of arming militants who "eat the organs" of their enemies.