The US has expelled two security guards at Iran's United Nations mission on suspicion of espionage.
New York is both a tourist attraction and a potential target
A US diplomat said the two Iranians had engaged in activities "incompatible with their stated duties" - diplomatic language for spying.
They were caught on three occasions over the past two years taking pictures of various New York City sites, another official told AP news agency.
They left the US in recent days, the official added.
He said the guards were first caught photographing infrastructure, transport facilities and landmarks in June 2002.
The second incident occurred in November 2003. After the two were stopped recently while taking photographs, the government expelled them, the official said.
Richard Grenell, a spokesman for the US mission to the UN, confirmed the expulsions but gave no details.
"We asked them to leave because we were very concerned about their activities, which were incompatible with their stated duties," he said.
Iran is one of seven countries designated by the US state department as sponsors of terrorism.