US Homeland Security Secretary Tom Ridge has charged Islamic cleric Abu Bakar Bashir is deeply involved in terrorism after Indonesia's top court halved the militant's jail sentence.

Ridge, speaking after talks with Indonesian security minister Susilo Bambang Yudhoyono, said Tuesday's Supreme Court ruling "obviously will be disappointing to the United States." "Hopefully in due time, at least from our country's point of view and appreciation of the intense and deep involvement of Bashir in both the execution and planning of terrorist activities ... at some point of time he will be brought to justice in a different way," Ridge said, without elaborating.

Indonesia told the visiting official it remained committed to fighting terrorism despite the court's decision, which also sparked dismay in Australia.

Bashir is said by foreign governments to have led the al-Qaeda-linked Jemaah Islamiyah (JI), a group which staged the Bali bombings in October 2002 and numerous other bloody attacks.

The court halved Bashir's three-year prison sentence for immigration and forgery offences. It said the time he has spent in detention counts towards his new 18-month sentence, meaning he could be free within weeks.

Yudhoyono said he respected the court's decision but the government would "continue our national effort to deter, to prevent and to defeat terrorism of any type and form." Australian Foreign Minister Alexander Downer insisted Bashir had been JI's spiritual leader. Eighty-eight Australians were among the 202 people killed in the Bali nightclub bombings of October 2002.

"If he's to be released, then that obviously would give Jemaah Islamiyah a bit of revitalisation," Downer said. It was Bashir's second legal victory after an appeal court last November cleared him of plotting to topple the government through JI terrorism.

"Bashir seems to live the charmed life," said a Straits Times editorial in Singapore, the first country to alert Indonesia in early 2002 about Bashir's alleged terror links.

The cleric was finally arrested in October 2002, a week after the Bali bombings. He was not accused of involvement in that attack.

When his trial began in April 2003, prosecutors alleged he headed JI, authorised the network's church bombings in Indonesia which killed 19 people on Christmas Eve 2000 and plotted to blow up US targets in Singapore.

Last September Bashir was convicted of taking part in a JI plot to overthrow the government but judges said there was no proof he had led the network. They jailed him for four years for treason and for immigration-related offences.

An appeal court in November overturned the treason conviction but ruled that Bashir must serve three years for immigration offences and forging documents.

Bashir, 65, says claims that he is linked to terrorism are part of a US and Jewish smear campaign against Islam. He says the Bali bombings were a CIA plot.

The cleric co-founded the al-Mukmin Islamic boarding school in Central Java from which numerous convicted terrorists including some of the Bali bombers graduated.

Bashir is still unhappy that the Supreme Court upheld his conviction on immigration and forgery offences despite the sentence cut, said one of his lawyers, Muhammad Assegaf.

Four lawyers visited Bashir at Jakarta's Salemba prison on Wednesday afternoon to discuss whether to seek a judicial review of the ruling.

Assegaf, speaking before the visit, said that "theoretically" the cleric should be freed early next month but police might seek to keep him jailed for about a month after that.

The two sides differ on when a formal detention order first went into effect.