Barack Obama on Wednesday began his first full day as the Democratic party’s presumptive presidential nominee by emphasising the option of using military force against Iran and calling on Israel to maintain Jerusalem as its undivided capital – despite ongoing peace talks with the Palestinians.

In a speech to an audience of 7,000 at the American Israel Public Affairs Committee’s annual meeting in Washington, Mr Obama tried to redefine his dispute with John McCain, his prospective Republican rival, over whether to talk to Iran and sought to win over doubting Jewish voters.