Iran on Thursday, February 4, called on the United States to make a clear public pledge that it would not penalize European banks for legitimate trade with the Islamic Republic, Reuters reports.

Many foreign banks are cautious about resuming trade with Iran following January's nuclear deal because they fear being caught up in ongoing U.S. sanctions.

"Rebuilding the confidence of the banks that the United States will not re-intervene in their relations with Iran may require some further assurance from the United States," Iranian Foreign Minister Mohammad Javad Zarif said at Chatham House in London.

"We don't need any more legalese - we need clear precise assurances that banks can do business with Iran," he said. "I hope that is fast coming because if not it would be a problem of implementation."

Although world powers lifted many crippling sanctions against Iran in return for the country complying with a deal to curb its nuclear ambitions, some restrictions remain in place

Washington still prevents U.S. nationals, banks and insurers from trading with Iran and also prohibits any trades with Iran in U.S. dollars from being processed via the U.S. financial system.

European banks are also cautious - with some, including Deutsche Bank, remembering past fines from U.S. regulators for breaking sanctions.