WASHINGTON - The United States hailed Friday Malaysia's arrest of a blackmarket nuclear agent, saying it could be a breakthrough in global efforts to dismantle Pakistani scientist Abdul Qadeer Khan's illicit nuclear network.

"We're delighted by the arrest," US State Department spokesman Richard Boucher told reporters. "This is decisive action that's been taken by the government of Malaysia."

"We think his arrest is a major step and it will serve as a catalyst to international efforts to shut down the Khan network."

Sri Lankan businessman BSA Tahir, described by President George W Bush this year as Khan's "chief financial officer and money launderer," was arrested Friday in Kuala Lumpur as a threat to national security, government officials said.

They gave no further details, but under Malaysia's wide-ranging Internal Security Act (ISA), Tahir can be held indefinitely without trial.

Khan, a one-time national hero credited with making Pakistan a nuclear power, has admitted selling nuclear secrets abroad but was pardoned by President Pervez Musharraf.

Arrest a surprise

Washington says it has received significant amounts of information from Pakistan about Khan's network and his activities and associates. Khan has also admitted to assisting North Korea's nuclear enrichment program.

The arrest of Tahir came as a surprise after government officials repeatedly said he had apparently not violated any regulations and was "a free man."

Boucher said Tahir "is one of the most important figures" in the Khan network," having served as chief financial officer and "essentially ran network operations.

He said the United States encouraged all states with individuals or companies tied to the Khan network to take similar action.

"So this is an action taken by the government of Malaysia. We think it's a good thing," he said.

A potential Malaysian link to the international nuclear blackmarket surfaced earlier this year after it was revealed that a company owned by Prime Minister Abdullah Ahmad Badawi's son Kamaluddin had manufactured centrifuge parts seized on a ship headed for Libya last year.

A police probe cleared the company, Scomi Precision Engineering (SCOPE), which said it had been misled about the purpose and destination of the parts, allegedly ordered by Tahir on behalf of Pakistan's Khan.

Tahir, 44, admitted to police that he acted as a middleman for Khan, and gave details of the proliferation scandal, according to an official report handed to the International Atomic Energy Agency in February.

Named as Khan's deputy

Tahir said Khan asked him to send centrifuges, which can be used to enrich uranium for nuclear weapons, to Iran in 1994 of 1995 and had told him that an undisclosed amount of enriched uranium was sent by air from Pakistan to Libya around 2001.

While naming Tahir as Khan's "deputy", Washington had not called publicly for his arrest.

Instead, it sent its top anti-proliferation official John Wolf to Malaysia in March to press for the imposition of more stringent export controls.

Malaysia is a signatory to the Nuclear Non-proliferation Treaty, which governs the movement of nuclear weapons materials, such as uranium, but it has not signed an additional protocol covering nuclear-related parts.

Malaysia said that it did not see the need to sign the protocol "at present". - AFP