From Barbara Starr
CNN Pentagon Correspondent

WASHINGTON (CNN) -- The Pentagon does not believe an Iranian rocket test over the weekend was successful, despite reports in the official Iranian media saying the Islamic Republic had launched its first vehicle capable of placing a satellite in orbit.

"The Iranians did not successfully launch the rocket," a senior U.S. defense official told CNN Monday.

The two-stage rocket could have been capable of launching a satellite into space, but the U.S. intelligence assessment shows that the second stage "was erratic and out of control," said the official, who declined to be identified because of the sensitivity of the intelligence.

The rocket "did not perform as designed," the official said.

Another U.S. defense official who also asked not to be named said the most immediate monitoring of the Iranian test came from the USS Russell in the Persian Gulf using its radar.

The U.S. assessment differs sharply from reports in the Islamic Republic News Agency which said the rocket launch was successful and "paved the way for placing the first Iranian satellite in orbit."

It is generally acknowledged that U.S. military and intelligence satellites have a long-standing capability to monitor rocket and missile launches around the world by detecting plumes and other launch emissions.

IRNA reported Sunday that the launch of the two-stage rocket, called Safir or "messenger," was successful on Saturday.

The reported test launch comes amid back and forth between Iran and Western powers on the country's controversial nuclear program.

Senior U.S. officials had expressed concerned over the weekend about the new reported test, saying Iran could use the rocket to deliver warheads.

"The Iranian development and testing of rockets is troubling and raises further questions about their intentions," said National Security Council spokesman Gordon Johndroe.

"This action and dual-use possibilities for their ballistic missile program have been a subject of (International Atomic Energy Agency) discussions and are inconsistent with their U.N. Security Council obligations."

Last month the U.S. cast doubt on Iranian reports of another missile test, saying at least one of four apparent launches in a widely reproduced photograph had not taken place. A U.S. military official who declined to be named suggested the photograph had been digitally altered to conceal the fact that one missile failed to launch.

Iran has been developing its space program for some time, but the extent of it remains unclear. In February, the country fired a rocket from its newly inaugurated space center, laying the groundwork for what it said would be the launch of its first domestically produced satellite, state-run media said at the time.

And in February 2007, state television announced that Iran successfully launched a rocket that carried research materials into space, but the report did not say if the rocket reached orbit. It said the payload carried by the rocket was "research material for the ministries of science and defense."

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