WASHINGTON (AP) — The United States on Tuesday imposed sanctions on Iran’s largest digital asset exchange, Nobitex, along with three other platforms, the Treasury Department announced, alleging the company has funneled billions of dollars in digital assets abroad to shield the Iranian regime’s wealth.

The Treasury Department said Nobitex processed more than 50% of all Iranian digital asset revenue last year and supports a vast Iranian sanctions evasion network. The sanctions also target Nobitex’s president and co-founder, Amir Hossein Rad.

The Treasury accused Nobitex of moving assets and funds outside the country to protect the regime’s wealth after the start of the war. A representative for Nobitex could not be reached for comment.

The sanctions were announced as a pair of semi-official Iranian news agencies reported Tuesday that Iran had stopped communicating with mediators about extending a ceasefire in the war with the United States and Israel. President Donald Trump disputed that claim, saying the talks are ongoing.

The U.S. has repeatedly expanded financial pressure on Iran in recent months. In May, the Treasury told U.S. banks to flag suspected Iranian money laundering networks, and the administration has sanctioned dozens of entities tied to Iranian oil shipments.