Iran has built a mock-up of a US Nimitz-class aircraft carrier, which experts believe could be blown up in a staged propaganda exercise.
Newly released commercial satellite images show the model under construction in a shipyard near Bandar Abbas on the Persian Gulf.
"They got this barge and threw some wood on top of it to make it look like the USS Nimitz. That's all we know for sure,' a US defence official told AFP.
Obama administration officials said that they did not know what the craft was for, and was not operational, but an attack on it could be staged for propaganda value.
The wooden craft was first spotted on the coast of the Persian Gulf last summer.
It is the same shape as US Navy Nimitz class aircraft carriers such as the USS Abraham Lincoln and the USS Carl Vinson, and has the same 68 painted in white just below the bow. However it is about as third of their 1,100 feet long.
Pictures also show fake aircraft parked on its deck.
The New York Times reports that the Iranian military has used fake boats for televised military exercises in the past, and if talks between the US and Iran on the Middle Eastern state's nuclear programme, could be towed out to sea and blown up in televised wargames.
Analysts do not believe that Iran has the capacity to build its own aircraft carrier.
"It is not surprising that Iranian naval forces might use a variety of tactics -- including military deception tactics -- to communicate and possibly demonstrate their resolve in the region," said another US official.
Tensions between the US and Iran have decreased recently, after Iran agreed partly to suspend its nuclear programme in exchange for a partial lifting of sanctions.