US officials are concerned that the craft's falling into Iran 's hands could lead to security breach, although they said the aircraft's technology cannot be engineered with ease.
The Iranian Foreign Ministry on Thursday summoned Swiss Ambassador to Tehran Livia Leu Agosti to protest the "violation" of its airspace by a US drone, the state IRIB TV reported.
Iran's protest letter denounced the growing US "provocative and secret moves" against the Islamic Republic, said the report.
"The move is in violation of all international conventions and runs counter to regional and international peace and security. Surely the responsibility for the illegal move lies with the US authorities," the letter was quoted as saying.
The letter added that Iran would reserve the right for following the case as deemed appropriate.
The Swiss embassy in Tehran represents the US interests in Iran since Tehran and Washington severed diplomatic relations in 1980.
US President Barack Obama said on Thursday that no options are off the table on Iran's nuclear program.
"No options off the table means I'm considering all options," the president told reporters at the White House.
In defense of his policy towards Iran, Obama said when he took office in 2009, the world was divided but Iran "was unified and moving aggressively on its own agenda."
In contrast, the Islamic Republic is isolated today while the world is unified and "applying the toughest sanctions that Iran's ever experienced," he argued, adding the sanctions are having an impact inside the country.
He vowed to work with US allies, including Israel, to prevent Iran from acquiring nuclear weapons.
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