A physician with New Zealand citizenship faces up to 30 years in prison after being caught by United States authorities supplying large quantities of fake erectile dysfunction drugs in the US and Europe.

US Immigration and Customs Enforcement (ICE) in California says Robin Han, 43, who pleaded guilty on Thursday to three federal charges, could also be fined up to $US6 million ($NZ7.5m).

ICE issued a statement saying Han will be sentenced on October 4 by US District Judge George Wu.

"Trafficking in counterfeit prescription drugs of any kind represents a serious threat to public safety," said US Attorney Andre Birotte Jr.

"The Department of Justice will continue to work with all of its law enforcement partners ... to help secure federal convictions that should send a strong message to international counterfeiters like Mr Han."

Han, who was living in China, was indicted in December 2007 but not arrested until March this year when he arrived at San Francisco International Airport from Hong Kong.

He has been in custody since then.

US authorities started investigating him in 2006 after intercepting a parcel from China that contained counterfeit Cialis tablets and fake Cialis packaging.

According to the case indictment, Han advertised the sale of counterfeit pharmaceuticals on a number of websites.

Homeland Security special agents made undercover purchases of about 20,000 counterfeit Viagra, Cialis and Levitra tablets with an estimated retail value of about $US200,000.

On the parcels Han shipped to the undercover agents, the packing slips falsely claimed the contents were plastic stationary holders and pen boxes.

NZN