(CNN) -- A New Zealand citizen has pleaded guilty to charges related to supplying large amounts fake erectile dysfunction drugs to distributors in California, Texas and Europe, U.S. authorities said Thursday.

The defendant, Robin Han, 43, is scheduled to be sentenced on October 4 in U.S. District Court in California, the U.S. Immigration and Customs Enforcement said in a statement. He faces as many as 30 years in prison and a fine of as much as $6 million.

U.S. authorities initially indicted Han, who was living in China, in December 2007. They did not arrest him until March of this year when he arrived at San Francisco International Airport from Hong Kong. Han has remained in federal custody since then.

The authorities had been on his trail since 2006 after Customs and Border Protection officers found a parcel from China containing counterfeit Cialis tablets and phony Cialis packaging at a mail facility in California.

The resulting investigation pinpointed Han as the source of the parcel.

The indictment against Han accuses him of advertising the fake drugs on several websites, including the Chinese e-commerce giant Alibaba.com.

Special customs agents discreetly purchased about 20,000 Viagra, Cialis and Levitra tablets with an estimated retail value of around $200,000, U.S. authorities said. Han sent the parcels using packaging slips that claimed they were plastic stationary holders and pen boxes.

In the plea agreement with U.S. prosecutors in California, Han has admitted to three counts of trafficking goods bearing counterfeit trademarks.

"Trafficking in counterfeit prescription drugs of any kind represents a serious threat to public safety," United States Attorney Andre Birotte Jr. said in the statement by U.S. authorities.