Israel's image in the United States may be tarnished and relations with its main ally suffer even if suspicions a Pentagon analyst gave secrets to the Jewish state prove false, Israeli officials said on Sunday.
Israel has strenuously denied spying after US government sources said the FBI was investigating whether an analyst fed classified documents dealing with bitter foe Iran via a powerful pro-Israel lobby group.
But Israelis voiced fears that just a hint of scandal may hurt links that have rarely been so close or so vital.
"Even if this is nonsense, it could still harm relations because of the damage in public opinion," said a senior Foreign Ministry official. "It will be very difficult to correct it."
Timing could be critical as Israel counts on Washington for backing over a unilateral plan to break from conflict with the Palestinians, to trump growing pressure over its West Bank barrier and to address fears that Iran could build an atom bomb.
Israeli officials insist that Israel has not spied on the United States since being caught red-handed two decades ago in a scandal involving US Navy analyst Jonathan Pollard - jailed for life in a case that is still an irritant in relations.
The powerful American Israel Public Affairs Committee also denied serving as a conduit for documents from the analyst connected to US Defence Secretary Donald Rumsfeld's office.
Official intelligence co-operation tends to be close, though, with both countries sharing fears of Islamic militancy and whether Iran will develop nuclear weapons. Tehran denies trying to build bombs to rival Israel's presumed nuclear arsenal.
The Washington Post said the investigation focused on an Iran specialist at the Defence Intelligence Agency who had once served in Israel. It was unclear whether the case would result in espionage charges or lesser charges, the report said.
Some Israeli officials suggested the leak of the Pentagon probe, just before the Republican party convention in New York, looked like a pre-election attempt to soil Jewish, pro-Israel "neo-conservatives" in President George W. Bush's camp who championed war in Iraq.
"What should be asked is who had a vested interest ... And that's where this gets serious - the effect it could have on the relations of the Jewish community in the United States," said Uzi Arad, a former official of spy agency Mossad.
Any dip in ties could be damaging for Israeli Prime Minister Ariel Sharon, who has highlighted his warm relations with Bush and visited the White House nine times since taking office.