Iran has rebuffed a US request for the return of a surveillance drone which came down in Iranian territory last week and called on Washington to apologise over the incident instead.
US President Barack Obama made the request in a press conference with Nuri al-Maliki, the Iraqi prime minister, at the White House on Monday.
"We have asked for it back. We'll see how the Iranians respond," said Obama.
But a spokesman for the Iranian foreign ministry on Tuesday accused the US of violating Iranian airspace, conducting a spying operation and trampling on international law.
"Instead of an official apology for the offence they have committed, he is raising such a demand. America must know that the violation of Iran's air space can endanger world peace and security," said Ramin Mehmanparast.
In an interview on Venezuelan state television, Iranian President Mahmoud Ahmadinejad said Iran had control of the plane and was analysing the aircraft's systems.
"The North Americans at best have decided to give us this spy plane. Currently, we have control of this plane. Those who have been been in control of this spy plane surely will analyse the plane's system. Furthermore, the systems of Iran are so advanced also, like the system of this plane.
"In the unpiloted planes, we have had many advances, much progress and now we have this spy plane," he said.
Iran lodged a formal complaint earlier this week to the UN over the entrance of a US drone "deep" into its eastern airspace last week, and aired footage of what it said was the high-tech US aircraft.
'Provocative and covert actions'
The Iranian foreign ministry summoned the Swiss ambassador and said the incident suggested Washington had upped its "provocative and covert actions" against Tehran, the state television website reported on Thursday.
The Swiss embassy handles US interests in the absence of Iran-US diplomatic ties.
The country called on the UN to condemn the "covert actions" that it said had increased and intensified in recent months.
In a letter to Ban Ki-moon, the UN secretary-general, Iran's ambassador to the UN said his government considered the drone incursions "tantamount to an act of hostility" and "violations and acts of aggression".
Iran "strongly protests the violation of an RQ-170 spy aircraft deep into its airspace," the letter said, adding that Tehran asked for "an urgent response and compensation from the US government".
Iranian media said late on Sunday that an RQ-170 unmanned aerial vehicle was shot down after making an incursion slightly into Iranian airspace. But no precise indication has been given by Iranian officials on where it crashed.
US media said the drone crashed in eastern Iran probably due to a malfunction.
The RQ-170 Sentinel is a high-altitude stealth reconnaissance drone made by Lockheed Martin, whose existence was exposed in 2009 by specialised reviews and later confirmed by the US Air Force in 2010.
US media have reported fears that Iran could access and make use of highly-advanced technology found in the drone.
The crash came at a time of heightened political tension over Iran's disputed nuclear programme, which Iran says is for peaceful purposes but the US and other Western powers believe is intended to build a nuclear bomb.