UNITED NATIONS - Iran sent letters protesting illegal overflights by two unmanned American aircraft that crashed in Iran in recent months, documents circulated at the United Nations on Monday showed.

Iran"s deputy U.N. ambassador Mehdi Danesh-Yazdi asked the U.N. Security Council on Oct. 26 to circulate two letters protesting "the violation of the territory and airspace of Iran by two American unmanned aircrafts."

The two letters, which were circulated Monday, warned that "the government of the United States of America will be responsible for the consequences of any recurrence of its unlawful acts."

According to the letters, during illegal overflights an American Shadow-200 aircraft crashed on July 4 about 38 miles inside Iranian territory in the province of Ilam, and an American Hermes aircraft crashed 125 miles inside Iranian territory in the Khoram Abad area on Aug. 25.

Defense Department spokesman Lt. Col. Barry Venable said the Pentagon had not yet seen Iran"s complaint and declined to comment further.

The United States and Iran have not had diplomatic relations since shortly after the Iran hostage crisis began in 1979. The letters were sent from Iran"s Foreign Ministry to the Swiss Embassy in Tehran, which represents the United States in the Islamic country.

One letter, dated Aug. 9, said Iranian authorities reported the crash of "an alien unmanned aerial vehicle" at sunset July 4 in Ilam province. It said "investigations on the wreckage ... indicate this is an American Shadow-200 (RQ-7) aircraft."

The other letter, dated Sept. 13, said Iranian authorities investigating the Aug. 25 crash of "an alien unmanned aerial vehicle" in the Khoram Abad area found that it was "an American Hermes aircraft."

"The government of the Islamic Republic of Iran strongly protests against such unlawful acts and emphasizes the necessity to observe the principles of international law concerning the sanctity of the sovereignty and territorial integrity of states, and calls for an end to such unlawful acts," both letters said.

The United States has become increasingly concerned about Iran"s nuclear ambitions. But Secretary of State Condoleezza Rice has quieted fears in Europe and elsewhere that the U.S. planned a second-term invasion or air strike to eliminate what it sees as a looming nuclear threat from the Islamic republic.

Although Rice has said the military option remains on the table, she has embraced European-led diplomacy. European negotiations with Tehran had stalled, leading to calls for tough U.N. sanctions, but Iran offered Sunday to resume talks on its nuclear program.