Washington: United States is "delighted" over the arrest in Malaysia of Sri Lankan businessman Buhary Syed Abu Tahir allegedly involved in the nuclear proliferation network of disgraced Pakistani scientist Abdul Qadeer Khan.

"We are delighted by the arrest, frankly. This is decisive action that has been taken by the Government of Malaysia," US State Department spokesman Richard Boucher said.

He said Tahir's arrest was a major step and it would serve as a catalyst to international efforts to shut down the Khan network.

"Tahir was one of the most important figures in the AQ Khan network. He served as Chief Financial Officer and essentially ran network operations," Boucher said.

He said that the United States was in touch with the Malaysian Government on all these issues, as well as other Governments, about the Khan network.

Asked whether the US Embassy in Pakistan had received any e-mailed threats said to involve hijacking of aircraft, Bloucher said, "I don't know specifically about that. I do know there are a variety of threats all the time and we consider so many places to be high-threat areas."