Jakarta – Five suspected members of Osama bin Laden's Al-Qaeda network arrived in Indonesia from Yemen last July with a plan to blow up the United States Embassy in Jakarta, a high-ranking US official has revealed. But Indonesian authorities balked at taking action, allowing the men to slip out of the country after they realised they had been discovered, said the official, who spoke on condition of anonymity.

US diplomats surmised that the authorities had intentionally scared the team away so as not to have to confront them. The incident, which was not made public earlier, highlighted the ambivalent attitude of Indonesia's government and military towards foreign and domestic Islamic radicals who reportedly assisted the Al-Qaeda team.

It also illustrated the difficulties the United States may face if it extends its war against Al-Qaeda and related terrorist groups to South-east Asia, where close cooperation with friendly governments and security forces would be essential for success.

In Washington, another US official confirmed that an Al-Qaeda plot to detonate a truck bomb at the US Embassy in Jakarta around July or August of 2001 was disrupted.

Indonesia's Security Minister Susilo Bambang Yudhoyono declined to comment on the allegations on Wednesday, but said law enforcement agencies were monitoring potential terrorists. Police chief Gen. Da'i Bachtiar said he had not received reports of the alleged plot.

In August, the presence of the suspected terrorists caused a partial closure of the US Embassy in Jakarta, although diplomats refused to identify the threat at the time. A hand-drawn sketch of the building allegedly in their possession "fit the pattern" of attacks on US missions in Kenya and Tanzania in 1998, the US official said.

But Indonesian authorities "took so much time to establish a wiretap, then brought in the local police and created so much noise", that this alerted the terrorists and local collaborators and gave them time to flee, he said.

The five men, who arrived from Yemen, had based themselves at a religious institution run by Arab Indonesians in eastern Java, the official said. The eastern city of Surabaya is home to tens of thousands of people of Arab descent. Most are immigrants from Yemen who maintain close ties to their homeland. The US became a target of terrorism in Yemen with the October 2000 suicide bombing attack on the destroyer Cole, which killed 17 sailors. That attack was blamed on the Al-Qaeda network.