MITT Romney has accused Barack Obama's White House of leaking national security secrets in order to bolster the President's reputation, in a major foreign affairs speech hours before he was due to arrive in London on the first leg of an overseas trip.
Addressing a Veterans of Foreign Wars convention, the presumptive Republican presidential candidate said: ''Whoever provided classified information to the media, seeking political advantage for the administration, must be exposed, dismissed, and punished.
''Exactly who in the White House betrayed these secrets? Did a superior authorise it?'' Mr Romney asked.
''These are things that Americans are entitled to know - and they are entitled to know right now. If the President believes - as he said last week - that the buck stops with him, then he owes all Americans a full and prompt accounting of the facts.''
Republicans and Democrats have complained for weeks about a series of leaks which led to explosive stories in US media, including one describing Mr Obama's alleged push for cyber-attacks on computers that run Iran's nuclear facilities.
''What kind of White House would reveal classified material for political gain?'' Mr Romney said. ''I'll tell you right now: Mine will not.''
Attorney-General Eric Holder has launched an investigation into the source of the leaks.
Mr Romney hopes to use his visits to Britain, Israel and Poland over the next week to counter the perception that he has a tenuous grip on foreign affairs. The Republican contender plans to attend the opening ceremony of the Olympic Games, providing an opportunity to remind US voters of his claim to have saved the 2002 Salt Lake City winter Games from meltdown.
Mr Romney's trip to Israel is the most likely to have political impact back home, not least as he attempts to rally conservative Christian evangelical voters who are strong supporters of Israel but sceptical about his Mormon faith.
Mr Romney used comments by the Democratic leader of the Senate intelligence committee, Senator Dianne Feinstein, to bolster his attack on the White House.
''I think the White House has to understand that some of this is coming from their ranks,'' she told a World Affairs Council forum on Monday.
Earlier yesterday Senator Feinstein released a statement reiterating that she did not believe the President was behind the leaks. ''I shouldn't have speculated beyond that, because the fact of the matter is I don't know the source of the leaks,'' she said.
In a speech that appeared to be designed to blunt any political advantage Mr Obama may have gained by authorising the killing of Osama bin Laden, Mr Romney also attacked the President for planned defence cuts and he described his foreign affairs stance as tougher than the President's.
''If you do not want America to be the strongest nation on Earth, I am not your President, you have that President today.
''Don't bother trying to find a serious military rationale behind any of this, unless that rationale is wishful thinking,'' Mr Romney said.
''Strategy is not driving President Obama's massive defence cuts. In fact, his own Secretary of Defence warned that these reductions would be 'devastating'. And he is right.''
The Vice-President, Joe Biden, responded to the speech in a statement. ''Over the past three years, President Obama has taken the fight directly to America's enemies, confronting al-Qaeda head on and taking out Osama bin Laden. He ended the war in Iraq responsibly and has a plan to do the same in Afghanistan,'' he said.