The probe goes beyond allegations that a single mid-level policy analyst gave a classified Iran policy document to Israel, to focus on other civilians working at the Pentagon, according to three officials familiar with the matter who spoke on condition of anonymity.

The Federal Bureau of Investigation has contacted the analyst and is seeking his cooperation in the investigation, The New York Times reported Sunday.

Reports Saturday identified him as Larry Franklin, an Iran specialist in the office of Undersecretary of Defense for Policy Douglas Feith, the third most senior civilian official at the Pentagon.

He is thought to have given Israeli lobbyists a draft of a top secret presidential order on Iran policy that ultimately was never completed due to disagreements among President George W. Bush's advisors. The lobbyists are alleged to have passed it on to their government.

Having a draft of the document would allow Israel to influence policy while it was being made. Iran is known to have funded militant groups within Israel and is high on the list of Israel's security concerns.

The FBI believes Franklin acted out of ideological support for the Jewish state rather than for money, according to a top US official who spoke on condition of anonymity.

Investigators are questioning employees of a powerful Washington lobby group, the American Israel Public Affairs Committee, which called allegations of its involvement "false and baseless."

They are also trying to determine whether Franklin acted with the authorization of his superiors.

The case drew terse comments from the US government and vehement denials from Israel.

"Obviously anytime there's an allegation of this nature it is a serious matter," White House spokesman Scott McClellan said Saturday, refusing to say more.

"We have no involvement in these allegations," a spokesman for Prime Minister Ariel Sharon's office told AFP in Jerusalem Sunday.

"It is an internal issue in the United States which is running out of steam anyway. Israel has not used an agent to spy on the United States, the country which is its best ally."

The Pentagon issued a two sentence statement late Friday saying that it "has been cooperating with the Department of Justice on this matter for an extended period of time.

"It is the (Department of Defense's) understanding that the investigation within the DoD is limited in its scope," the statement said.

Other sources differed, saying the probe involved interviews of current and former officials at the White House, Pentagon and State Department, concerning security practises of Defense Department civilians.

Since June, federal agents have been investigating whether Pentagon officials gave classified information to former Iraqi exile leader Ahmed Chalabi.

Feith's office had close ties to Chalabi and advocated the now-discredited theory that Saddam Hussein had ties to Al-Qaeda, an argument used to push the case for war. Feith's office was also instrumental in post-war planning, now seen seen as inadequate.

No one has been charged in the current investigation although reports say arrests could come as early as next week. Charges may involve mishandling of classified material rather than the more serious charge of espionage.

Israel pledged not to spy on the United States after the case of Jonathan Pollard, an intelligence analyst for the US Navy, who passed on thousands of secret documents in 18 months before his arrest in November 1985.

Pollard was sentenced to life imprisonment in 1987, but Israel only admitted that he was one of its spies 11 years later. It has since lobbied Washington to grant him a pardon.