(Reuters) – U.S. prosecutors charged a man from Sierra Leone with trying to sell undercover agents 1,000 tons of yellowcake uranium he thought would be shipped to Iran, after he was arrested in New York with a sample of the toxic material hidden in his luggage.

Patrick Campbell, 33, of Freetown, was arrested at John F. Kennedy International Airport on Wednesday after he arrived from Sierra Leone with the sample of uranium concealed in the soles of shoes in his luggage, according to a criminal complaint filed in a Florida federal court on Thursday.

He allegedly responded to an ad in May 2012 on the website Alibaba.com seeking to purchase uranium that was placed by an undercover U.S. agent posing as an American broker representing persons in Iran, according to an affidavit by Homeland Security Investigations agent Louise Miller.

Campbell agreed to travel to Miami to meet the supposed buyer, who could then analyze the purity of the uranium.

Campbell made an initial court appearance in New York on Thursday. He faces up to 20 years in prison and a $1 million fine if he is found guilty of violating U.S. sanctions against Iran as well as the International Emergency Economic Powers Act.