Abdul Qadeer Khan has been under virtual house arrest since 2004
The US has imposed sanctions on people and companies linked to the former head of Pakistan's nuclear programme, the disgraced scientist Abdul Qadeer Khan.
The state department said 13 people and three companies would be targeted for their alleged involvement in Mr Khan's illicit trading of nuclear technology.
US officials said they hoped the sanctions would "help prevent future proliferation-related activities".
Mr Khan admitted transferring nuclear secrets to other countries in 2004.
He was later pardoned by former Pakistani President Pervez Musharraf and has been under virtual house arrest in Islamabad ever since.
In July, Mr Khan told the media that Pakistan had transported uranium enrichment equipment to North Korea in 2000 with the full knowledge of the country's army, then headed by Gen Musharraf.
The former leader has repeatedly stated that no-one apart from Mr Khan had any knowledge of the transportation of nuclear technology.
'No longer operating'
In a statement, the US state department said that sanctions would be imposed on 13 individuals and three private companies "for their involvement in the AQ Khan nuclear proliferation network".
"We believe these sanctions will help prevent future proliferation-related activities by these private entities, provide a warning to other would-be proliferators," it said.
"While we believe the AQ Khan network is no longer operating, countries should remain vigilant to ensure that Khan network associates, or others seeking to pursue similar proliferation activities, will not become a future source for sensitive nuclear information or equipment."
The sanctions followed a US government review of information about the network, the state department added.
The individuals targeted include British, German, Turkish, Swiss and Sri Lankan nationals.
One of them, German engineer Gotthard Lerch, was sentenced last year to five-and-a-half years in prison for breaking export and weapons laws by sending uranium-enrichment equipment to Libya.
Last year, a UN nuclear watchdog said the AQ Khan network had smuggled nuclear weapon technology to Iran, Libya and North Korea and had been active in 12 countries.