The missile, called Shahab-3, was first tested in 1998 and has a range of 806 to 930 miles, which means it can reach Israel and American troops stationed in Saudi Arabia and Iraq.

The spokesman, Hamidreza Assefi, was responding to a report in the Israeli newspaper Haaretz last week, which said the test had been carried out just over a week before.

"Apparently, the Israelis are late in getting the information," Mr. Assefi said at the Iranian Foreign Ministry's weekly news briefing. "The test took place several weeks ago, and it was a final test before delivering the missile to the armed forces. It was within the same range that we had declared before."

Iran contends that the missile relies entirely on Iranian expertise, but it is widely believed that the Shahab, or shooting star in Persian, employs North Korean technology. The United States Department of State imposed penalties on a North Korean company and five Chinese companies last week, saying they sold missile technology to Iran.

"We are very concerned, especially since we know that Iran is seeking to acquire the nuclear weapon," an Israeli government spokesman, Avi Pazner, said immediately after the Iranian confirmation, according to a report from Agence France-Presse.

"The combination of Shahab-3 and the nuclear weapon would be a very serious threat on the stability of the region," he added, according to the report. 

The United States said today that it had "very serious concerns" about Iran's missile programs and that it viewed them as a threat to the region and to American interests. But American officials said that the latest test flight was one of several in recent years and that it was not a particular surprise.

"We have long had very serious concerns about Iranian missile programs," said Richard A. Boucher, the State Department spokesman. He said the United States had noted Iran's efforts to develop its missile abilities for nearly two decades.

He said that the missile program was "a threat to the region and a threat to U.S. interests in the region" but that it would be addressed with diplomatic, political and economic pressure with "like-minded countries" along with other Iranian activities, including its nuclear weapons program.

Last month, the International Atomic Energy Agency declared that Iran had secretly processed nuclear material. Iran has denied those accusations, insisting that its nuclear research is meant only for peaceful purposes like energy.

Foreign Minister Jack Straw of Britain, during a visit to Iran last month, said the European Union would cut trade ties with Tehran if it refused to open its sites to inspections.

Dr. Mohamed ElBaradei, the director of the International Atomic Energy Agency, is scheduled to visit Iran on Wednesday. He is expected to urge the Iranians to sign a protocol that would allow the agency's inspectors to make surprise visits to nuclear sites and to take samples.