Larry Franklin, a mid-level Pentagon analyst, has emerged as the man at the centre of an FBI investigation into the possible transfer of US classified information to the Israeli government. But the political target of the allegations may prove to be his boss, Douglas Feith.
Officials have acknowledged an inquiry is under way into allegations that classified documents were passed to the American Israel Public Affairs Committee, an influential lobby group, which in turn passed the documents on to the Israeli government.
Mr Franklin was identified in US newspaper reports over the weekend. A former Defense Intelligence Agency official whose expertise is Iran, he worked in the Pentagon policy group led by Mr Feith the undersecretary of defence for policy, who has become one of the most controversial figures in Donald Rumsfeld's Pentagon.
Before he was recruited to the Bush administration, Mr Feith was known as a pro-Israeli, neo-conservative. Together with Richard Perle, also a prominent neo-conservative, Mr Feith wrote a paper in 1996 for Benjamin Netanyahu, then Likud prime minister, urging him to abandon the Oslo accords and reject the principle of giving up land for peace.
Inside the Pentagon, Mr Feith has been in charge of the Office of Special Plans, a unit established to work on Iraq intelligence. Critics have accused the unit of seeking to manipulate the intelligence to bolster the case for war in Iraq, in particular by building the case that Saddam Hussein's regime had al-Qaeda ties.
Mr Franklin participated in secret meetings in Europe in 2001 with Manucher Ghorbanifar, who offered a back-channel to Iranian dissidents. Mr Ghorbanifar is alleged to have acted as a middle man in the arms deal at the centre of the Iran-contra affair in the 1980s.
The espionage allegations have been met with puzzlement by many experienced US government officials, who point out that AIPAC is arguably the most effective and best connected lobby group in Washington. If it wanted to find out about Iran policy, it could pick up the telephone to senior members of the government in the White House, the Pentagon or the State Department.
Israeli officials have strenuously denied the existence of a mole, insisting Israel has maintained its unilateral ban on spying on its closest ally since Jonathan Pollard, a US navy analyst, was convicted of espionage and sentenced to life imprisonment in 1985. The US has rejected Israeli calls for a pardon for Mr Pollard, who passed on classified information about alleged Syrian military threats to Israel.
Israeli commentators and analysts linked the leaking of the FBI investigation to possible attempts by political rivals to discredit President George W. Bush's decision to go to war in Iraq.
Critics of the war have alleged that pro-Israeli neo-conservatives, notably Mr Feith, pushed for the invasion of Iraq because the collapse of Mr Hussein's regime served Israel's interests.
?Whoever leaked the information knew it would exacerbate this canard,? said Michael Oren, an expert in US-Israeli relations at Jerusalem's Shalem Centre. ?Whoever wanted to hurt Bush at this time has done a good job.?
Mr Oren said the allegations, if substantiated, would have a grave impact on bilateral relations and would compromise the position of AIPAC.