U.S. officials are tracking Iranian attempts to secretly buy out banks in Muslim countries to evade sanctions triggered by Iran's refusal to give up its nuclear weapons program, the Washington Post reports.

The efforts are "an indication that they can't do normal banking," an unnamed senior administration official told the newspaper. The U.S. has blacklisted 16 Iranian banks as part of a sanctions package targeting

Iran has set up banks in Iraq and Malaysia using front companies, the Post reports.

The Treasury Department is aggressively hunting down evidence of secret Iranian bank efforts, sending officials to at least five countries, including Turkey and the United Arab Emirates, and warning "local authorities of the risks of letting these operations take root," the U.S. official told the Post.