WASHINGTON – The Treasury Department slapped sanctions Thursday on an Iranian businessman and a network of banks and companies dealing with Tehran amid an international stalemate over Iran’s disputed nuclear program.

The move targeted Babak Zanjani, along with a Malaysian bank and an international network of companies that U.S. officials said had moved billions of dollars on behalf of the Iranian regime.

Zanjani is chairman of the Sorinet Group of banks and companies that Tehran used as intermediaries to sell oil on the world market, the Treasury announcement said. His group is based in Dubai, United Arab Emirates, and includes front companies in Turkey, Malaysia and Tajikistan, it said.

The sanctions, which bar access to the U.S. financial system, are part of Washington’s ever-growing economic crackdown on Iran.