U.S. authorities are investigating Royal Bank of Scotland (RBS.L [1]) over possible breaches of sanctions on Iran [2], as part of a crackdown in which Standard Chartered (STAN.L [3]) has already agreed to pay a heavy fine for transactions involving Tehran.

An RBS spokeswoman referred on Wednesday to disclosures alongside the bank's half-year results earlier this month. These stated that RBS had initiated talks with U.S. and UK authorities on whether it complied with economic sanctions on Iran, and that it could face a material impact from the investigation.

Standard Chartered last week agreed to pay $340 million to the New York bank regulator over transactions linked to Iran. The British bank had been accused by the New York Department of Financial Services of concealing $250 billion in Iranian transactions.

In 2010, RBS agreed to pay $500 million to ... >>>