Gates was asked about the reports during congressional testimony.
He said that the successful test involved a missile with a range of approximately 2,000 to 2,500 kilometers. He said that because of chronic engine problems, the range is probably on the lower end of that scale.
Gates said he couldn't say whether the test missile hit its intended target.
Earlier Wednesday, Iran's President Mahmoud Ahmadinejad said the launch was a successful test-firing of a new advanced missile with a range of about 1,200 miles, capable of reaching Israel and U.S. Mideast bases.
The announcement comes less than a month before Iran's presidential election and just two days after President Barack Obama declared a readiness to seek deeper international sanctions against Tehran if it did not respond positively to U.S. attempts to open negotiations on its nuclear program.
"Iran's long range missile test is not only provocative, but it puts both President Obama and the Security Council in a difficult position," said CBS News foreign affairs analyst Pamela Falk from the U.N. "After three rounds of sanctions that have not worked, the best hope for a peaceful settlement continues to be for Iran to negotiate its way back to an inspections program."
"With Iran's election in less than a month, the situation might change," added Falk. "But Israel's new Prime Minister is pressing for more U.N. sanctions and Iran's current President Mahmoud Ahmadinejad is more defiant than ever."
Some dozen hours after the test, numerous U.S. defense and intelligence officials declined to even acknowledge the Iranian launch had occurred. Some referred calls to the White House and State Department, a sign of how politically sensitive the development is to the Obama administration and its continuing efforts to deal with Iran's reported efforts to build nuclear weapons.
But Gates confirmed the test's success Wednesday afternoon.
Secretary of State Hillary Rodham Clinton, apppearing Wednesday before the Senate Appropriations Committee, said that a nuclear-armed Iran isin the Middle East.
Without commenting directly on the missile launch reports, Clinton referred Wednesday to a host of threats to the United States that she said are "daunting."
Clinton reiterated that the Obama administration opposes Iran getting a nuclear weapons capability and that it is relying for now on diplomatic pressure to stop it.
She described a nuclear capability as an "extraordinary threat." And Clinton said that the U.S. goal is "to persuade the Iranian regime that they will actually be less secure if they proceed with their nuclear weapons program."
Iran continues enriching uranium, although not yet to bomb-grade levels. The CIA estimates Iran could have a nuclear weapon sometime between 2010 and 2015. But both the U.S. and Israel have launched covert operations designed to through sand in the gears by supplying faulty parts or designs, reports CBS News correspondent David Martin.
Clinton has indicated that Iran may be experiencing delays, saying, "Recent analyses have suggested the timetable may be longer than what originally had been thought."
But President Obama told Israel's new prime minister he is prepared to give diplomacy several more months to produce results.
U.S. officials are hoping for a more moderate government after elections in June. But the real powers in Iran are the mullahs and they aren't up for election, Martin reports.
Iran said the solid-fuel Sajjil-2 surface-to-surface missile is a new version of the Sajjil missile, which the country said it successfully tested late last year and has a similar range. Many analysts said the launch of the solid-fuel Sajjil was significant because such missiles are more accurate than liquid fuel missiles of similar range, such as Iran's Shahab-3.
"Defense Minister (Mostafa Mohammad Najjar) has informed me that the Sajjil-2 missile, which has very advanced technology, was launched from Semnan and it landed precisely on the target," state radio quoted Ahmadinejad as saying. He did not name any future targets for the missile when he spoke during a visit to the city of Semnan, 125 miles east of the capital Tehran, where Iran's space program is centered.
Najjar said the Sajjil-2 differs from the Sajjil missile because it "is equipped with a new navigation system as well as precise and sophisticated sensors," according to Iran's official news agency.
Sajjil means "baked clay." It is a reference to a story in the Quran, Islam's holy book, in which birds sent by God drive off an enemy army attacking the holy city of Mecca by pelting them with stones of baked clay.
Ahmadinejad is running for re-election and has been criticized by his opponents and others for antagonizing the U.S. and mismanaging the country's faltering economy. Iran said Wednesday that its constitutional watchdog has approved three prominent candidates to challenge Ahmadinejad, setting up a showdown between reformists and hard-liners.
Iran's nuclear and missile programs have alarmed Israel. The country's new prime minister, Benjamin Netanyahu, pressed Obama to step up pressure on Tehran when the two met in Washington on Monday. Israeli officials had no immediate comment on the Iranian missile launch.
Moshe Arens, a former Israeli defense minister who trained in the U.S. as an aerospace engineer, said Wednesday's test was apparently part of Iran's broader quest to develop more advanced missiles and nuclear capability.
"They're increasing their abilities to launch rockets of longer and longer range that go beyond Israel and into Europe and eventually will carry nuclear weapons," he said. "They're troublemakers and you have to deal with troublemakers."
Ahmadinejad has repeatedly called for Israel's elimination, and the Jewish state has not ruled out a military strike to deal with the Iranian nuclear threat. The Israeli government has been skeptical of U.S. overtures to Iran, which have received a mixed response from Ahmadinejad.
Many Western experts have expressed skepticism about Iran's professed military achievements, saying the country provides no transparency to verify its claims. Most believe Iran does not yet have the technology to produce nuclear weapons, including warheads for long-range missiles.
The U.S. released an intelligence report about 18 months ago that said Iran abandoned a secret nuclear weapons program in 2003 under international pressure and has not restarted it.
Israel and several other countries have disputed the finding. But many in the West at least agree that Iran is seeking to develop the capability to develop weapons at some point. A group of U.S. and Russian scientists said in a report issued Tuesday that Iran could produce a simple nuclear device in one to three years and a nuclear warhead in another five years after that.
The study published by the nonpartisan EastWest Institute also said Iran is making advances in rocket technology and could develop a ballistic missile capable of firing a 2,200-pound nuclear warhead up to 1,200 miles "in perhaps six to eight years."
Iran says its missile program is merely for defense and its space program is for scientific and surveillance purposes. It maintains that its nuclear program is for civilian energy uses only.
After the testing of the Sajjil in November, a senior U.S. military official said Washington believed Iran was testing the first stage of what would be a two-stage rocket. Multiple stages allow long-range missiles to use less fuel.
Ahmadinejad touted the launch in the final weeks of a presidential campaign that could influence Iran's response to the U.S. outreach. Two of the three candidates approved by Iran's constitutional watchdog to run in the June election are reformists who favor improving ties with the West.
Hard-liners have used the Guardian Council in the past to block reformist candidates, but Mir Hossein Mousavi and Mahdi Karroubi were likely too high-profile to reject. The watchdog also approved a well known conservative candidate, Mohsen Rezaei, a former leader of Iraq's elite Revolutionary Guards who has joined his reformist competitors in criticizing Ahmadinejad for mismanaging Iran's economy.
The group rejected 471 other candidates who wanted to run, including illiterate peasants, a 12-year-old boy and 42 women, the Interior Ministry said in a statement.
Reformists, who believe they have a strong chance of defeating Ahmadinejad, have criticized the president for spending an inordinate amount of time and energy slamming the West. They say his behavior has isolated Iran and believe he should have focused on battling rising unemployment and inflation in the country.
Mousavi, a former prime minister who is seen as the leading challenger to Ahmadinejad, has said he would reshape Iran's policies and restore the country's dignity.