The United States says it has no plans to give Iran access to the U.S. financial system in any dollar-denominated transactions between Iran and businesses in other countries.
State Department spokesman Mark Toner said certain sanctions would have to be lifted first. Under current sanctions, Iran is barred from any direct dealings with U.S. banks and investment houses.
Toner referred to President Barack Obama's comments last week that businesses that do want to deal with Iran in dollars could do so through European banks.
Iran has complained that its badly battered economy has not yet seen any benefits after some sanctions were lifted when a deal was signed to curb its nuclear program.
Obama said that so far, Iran has followed the letter of the nuclear deal. But he said last week that its "provocative" actions may be scaring off businesses.
"When they [Iran] launch ballistic missiles with slogans calling for the destruction of Israel, that makes businesses nervous," he said.