A Russian spy aircraft was spotted near Iranian airspace, a US official told Al Jazeera.
“The Russian plane was spotted at 9:30am local time, about 500 km from Iran’s territorial waters,” said US Army Col Kevin McKeon.
“It flew south into Iran’s airspace and then turned north,” he added.
“We’re currently assessing the situation.”
McKean told the news agency the US military was concerned about a possible collision between the plane and Iranian surveillance aircraft.
Iran has been conducting an aerial surveillance campaign against the US-led coalition and its allies since the start of the war in Iraq in 2003.
The US has repeatedly denied that it is seeking to use Iranian aircraft to spy on US allies.
The Iranian government has repeatedly stated it has no intention of using its aircraft for such operations.