Barack Obama focused on unifying a fractured party for the five-month battle for the White House last night and announced a high-profile three-person team to head the search for a running mate.

Barack Obama focused on unifying a fractured party for the five-month battle for the White House last night and announced a high-profile three-person team to head the search for a running mate.

Mr Obama clinched the Democratic nomination on Tuesday and will be the first black candidate to lead a major US party into a White House race. His last Democratic rival, Hillary Clinton, refused to concede but called it "an honour" to have competed against him.

Mrs Clinton's supporters turned up the pressure for the New York senator to be named as Mr Obama's No. 2, but Mr Obama's aides said the search process was just beginning.

In a speech, Mr Obama tried to smooth relations with Mrs Clinton after their long and sometimes bitter nominating fight, calling her an "extraordinary candidate and extraordinary public servant".

Mrs Clinton, in a later speech, complimented her opponent: "It has been an honour to contest these primaries with him. It is an honour to call him my friend."

Mr Obama sought to face down criticism from George W Bush and Republican presidential nominee John McCain that he is soft on foreign policy by declaring his "unshakeable commitment" to Israel's security and insisting he would do everything he could to stop Iran acquiring nuclear weapons.

"As president I will never compromise when it comes to Israel's security," he told the annual gathering of the American Israel Public Affairs Committee (AIPAC), a major Jewish lobby group.