President Barack Obama's point person on cracking down on financial flows to Iran resigned on Monday, marking the loss of a key player in the US effort to pressure Tehran over its nuclear program.
The departure of Stuart Levey from his role as the Treasury Department's under secretary for terrorism and financial intelligence could leave a hole in the US effort to discourage foreign companies and governments from doing business with Tehran.
As a holdover in the job from President George W. Bush's administration, Levey had built up personal relationships with officials in foreign capitals, and the Obama administration had viewed his efforts as highly successful.
Levey will be replaced by a deputy, David Cohen. US officials emphasised they did not think the staff change would stem the momentum for the drive to put the financial squeeze on Iran or for the separate task of trying to choke off access by militant groups to international sources of money.