Former US president Bill Clinton’s administration had enough evidence of Iran’s sponsorship of a deadly terror attack in Saudi Arabia to prompt a communique to the Iranian president, but kept the information under wraps to avoid demands for a more forceful response, the Washington Times reported on Tuesday.

Memos from the period before Clinton left office reveal that intelligence had indicated Iranian involvement in the 1996 bombing of the Khobar Towers, which killed 19 US servicemen.

As a result, in 1999, the administration sent a secret cable to then Iranian president Mohammad Khatami pointing out that the US knew who was behind the attack.

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A declassified copy of the cable from the National Security Archives group shows the US listed the Iranian Revolutionary Guard Corps and the Lebanon-based Hezbollah militia as the culprits.

“Message to President Khatami from President Clinton: The United States Government has received credible evidence that members of the Iranian Revolutionary Guard Corps. (IRGC) along with members of Lebanese and Saudi Hizballah [sic] were directly involved in the planning and execution of the terrorist bombing in Saudi Arabia of the Khobar Towers military resident complex,” the cable read.

“The United States views this in the gravest terms,” the message noted. “We acknowledge that the bombing occurred prior to your election. Those responsible, however, have yet to face justice for this crime. And the IRGC may be involved in planning for further terrorist attacks against American citizens. The involvement of the IRGC in terrorist activity and planning aboard remains a cause of deep concern to us.”

Not only was the information kept from the public; it was also suppressed within the US intelligence community, the report said.

The evidence was based on interviews with some half a dozen Saudi suspects, who told investigators they were provided with passports by the Iranian embassy in Syria, that an Iranian general was their handler for the attack, and that they were trained by the Revolutionary Guards.

A spokeswoman for Clinton wouldn’t comment, the report said.

A key suspect in the bombing was arrested in August. Ahmad Ibrahim al-Mughassil, who is wanted by the US Federal Bureau of Investigation, is said to head the military wing of Saudi Hezbollah, an outlawed organization whose members are drawn from the kingdom’s Shiite Muslim community.

The 48-year-old suspect was detained in Beirut and sent to Saudi Arabia, where he is being interrogated, the Saudi-owned Asharq al-Awsat daily said, quoting unnamed officials.

There was no immediate confirmation from Saudi authorities.

The massive bomb, which also wounded more than 370 people, destroyed part of the eight-story Khobar Towers in the eastern Saudi town of Dhahran in June 1996.

US prosecutors have said that Mughassil drove an explosives-laden truck and parked it outside the military compound before the attack.

The FBI has offered a reward of up to $5 million for information leading directly to his apprehension or conviction.

The Khobar Towers dormitory complex housed US, British, French and Saudi military personnel attached to the nearby King Abdul Aziz airbase.

AFP contributed to this report.