Australia has blamed human error after its leading intelligence agency ignored phone calls from an al-Qaida-linked terrorist seeking to expose the group's activities. The failure came to light after the Muslim convert pleaded guilty to conspiring to bomb the Israeli embassy in Canberra.

During his trial, 50-year-old Jack Roche said he had changed his mind in 2000 about carrying out an attack on the Israeli embassy, and tried to contact the Australian Security Intelligence Organization, or ASIO.

He said no one returned his calls, and he eventually gave up.

Terrorism expert Clive Williams says that had Roche's warning been taken seriously, it might have helped head off the bombings on the Indonesian island of Bali two years later, in which 88 Australians died. Those bombings were carried out by the Southeast Asian Muslim organization called Jemaah Islamiyah, or JI.

"Had we known a bit more about JI and its linkages to al-Qaida and what it was planning to do, maybe we could have put a bit more pressure on the Indonesians to put more effort into monitoring JI, which in turn might have made it much more difficult for JI to actually conduct its operations," said Mr. Williams.

Roche is the first Australian to be convicted under anti-terror laws passed after the September 11, 2001 terrorist attacks in the United States. In a dramatic U-turn 10 days into his trial, the English-born Muslim convert changed his plea on Friday to guilty.

Roche told a court in Perth that he became involved in militant Islam in Australia during the late 1990s. He traveled to Afghanistan in early 2000 and met al-Qaida leader Osama bin Laden, and also the man called Hambali. Hambali is accused of masterminding the Bali bombings 19 months ago.

Roche testified that he agreed to carry out terrorist actions in Australia. He said that while conducting surveillance of Israeli targets in late 2000, he began to have second thoughts, but feared al-Qaida operatives would kill him if he backed out.

After becoming increasingly disillusioned and afraid, Roche told the court he contacted the intelligence agency, trying to warn it of potential terrorist attacks by al-Qaida and Jemaah Islamiyah.

He said despite several phone to calls to ASIO, his offer of help and information was never taken up.

Australian Prime Minister John Howard on Sunday blamed the oversight on 'human failure' within the organization, but defended ASIO's performance and insisted he still had faith in it.

ASIO has changed its procedures as a result of the Roche affair.

Roche is due to be sentenced on Tuesday and faces up to 25 years in jail.