Iran this week conducted the first launch of a new rocket that the Pentagon views as a key element of Tehran’s effort to build long-range missiles.

The launch of the Simorgh space launch vehicle on Tuesday was judged by U.S. intelligence agencies to be partly successful but did not reach orbit, said defense officials familiar with reports of the test.

"It was either an unsuccessful launch, or a test of third stage" not meant to place a satellite in orbit, said a U.S. defense official familiar with reports of the test.

No other details of the test launch could be learned.

At the State Department, spokesman John Kirby said he could not confirm the missile launch.

"Obviously we're watching this as best we can," Kirby said. "Certainly if it's true and we're talking about a ballistic missile launch or the testing of ballistic missile technologies, that's obviously of concern to us. It's not consistent, as we said before, with the Security Council resolution…"

The large liquid-fueled rocket has been under close surveillance by U.S. satellites and other intelligence assets at a launch pad at Iran’s Semnan satellite launch center, located about 125 miles east of Tehran.

The Simorgh launch had been anticipated since March and comes amid growing worries about Iran’s development of long-range missiles.

Sen. Tom Cotton (R., Ark.) said he is concerned about the latest Iranian missile development.

"An Iranian Simorgh space launch vehicle test would be a provocation of the highest order and shows Iran’s true intentions," Cotton told the Washington Free Beacon.

"The intelligence community has said publicly that this [space launch vehicle] technology would aid an Iranian [intercontinental ballistic missile] program. And the only reason one develops ICBMs is the delivery of nuclear weapons," Cotton added.

Strategic Command spokesman Lt. Col. Martin O'Donnell said the command's Joint Functional Component Command for Space, which tracks thousands of orbiting objects in space, did not monitor any new objects reaching orbit on Tuesday.

The Simorgh is believed to be based on North Korean missile technology, used extensively in Iran’s medium-range Shahab-3 missiles. U.S. intelligence agencies believe North Korea supplied Iran with design data, stage separation technology, and booster equipment for the Simorgh and other rockets.

During negotiations on the Iran nuclear deal, U.S. intelligence agencies detected two shipments of large diameter rocket engines from North Korea to Iran.

The Simorgh also is assessed as having enough lift to carry a nuclear warhead, a throw-weight greater than the 220-pound payload capacity claimed by Iranian officials.

Senior U.S. military officials have voiced concerns about the Simorgh in recent congressional testimony and other public statements.

Adm. Bill Gortney, commander of the U.S. Northern Command, told a House hearing last week that Iran is continuing development of long-range missiles.

"Iran’s continuing pursuit of long-range missile capabilities and ballistic missile and space launch programs, in defiance of United Nations Security Council resolutions, remains a serious concern," Gortney said in prepared testimony.

"Iran has successfully orbited satellites using a first-generation space launch vehicle and announced plans to orbit a larger satellite using its ICBM-class booster as early as this year. In light of these advances, we assess Iran may be able to deploy an operational ICBM by 2020 if the regime choses to do so."

Air Force Lt. Gen. Jay Raymond, deputy chief of staff for operations, told reporters last month the Iranian space launcher is a "dual-use" system with applications for missiles.

"The concerning part to me is that the rocket that they use, that launch satellite, could … [have] a dual-use purpose," Raymond said March 24. "The ability to put a satellite into orbit is the same capability … as a harmful missile."

Vice Adm. James Syring, director of the Missile Defense Agency, also said the Simorgh could be used as a long-range missile.

"Iran has successfully orbited satellites and announced plans to orbit a larger satellite using a space launch vehicle, the Simorgh, that could be capable of intercontinental ballistic missile ranges if configured as such," Syring told the House Armed Services subcommittee on strategic forces last week.

Rep. Mike Rogers (R., Ala.), the subcommittee chairman, mentioned the Simorgh last week as an ICBM ready for launch.

Criticizing President Obama’s cuts in missile defenses for years, Rogers said: "America’s enemies know an opportunity when they see one; our allies see they are on their own. And the president proposed a nearly 10 percent reduction in missile defense compared to last year’s budget request. What does he think, the Iranians have a Simorgh ICBM on the launch pad because the mullahs want to go to the moon? My subcommittee will continue to fight the president’s priorities and policies until we get some relief next year."

The Simorgh was identified by defense officials as a covert missile that has been developed as a space launcher to mask the development.

Iran’s space program has included the launch of four satellites that were placed in orbit between 2009 and last year.

Based on a mockup displayed by the Iranians, the Simorgh appears to be a two-stage space launcher,

Laura Grego, a defense analyst at the Union of Concerned Scientists, said the first Simorgh was slated for launch in March. "As far as I can tell, Iran does not tend to acknowledge failures," she said of the lack of official Iranian acknowledgement of Tuesday’s failed launch.

Grego disagrees with military officials about the missile capabilities of the Simorgh.

"The Simorgh appears designed specifically as a satellite launcher, not as a ballistic missile, although some of the technology used in it could be used for a ballistic missile," she said, adding that it would take significant time to convert the satellite launcher to a ballistic missile.

Iran also lacks nuclear weapons and has not tested a heat-shielding re-entry vehicle, a necessary element of a reliable nuclear missile, she said.

However, Iran has cooperated in the past with North Korea, which recently demonstrated a heat shield for a warhead and showed off what appeared to be a small nuclear warhead that could be placed on a missile.

Rogers asked both Gortney and Syring last week about Iran’s missile programs and whether the recently concluded nuclear agreement with Iran had limited missile development.

Gortney said Iran’s nuclear program may be limited by the international agreement but there has been no change in its missile program.

"We see them continue to develop their propellant, the rocket motor, and we assume they're continuing to develop a reentry vehicle," Gortney said.

"So we see of the three pieces that they need, a nuclear weapon miniaturized to put on it, a delivery capable booster, and reentry vehicle. We don't see the latter two being slowed."

Syring added: "I agree. I do not see it slowing in any way."

The attempted launch of the Simorgh also appears to have violated the United Nations resolution on the Iran nuclear agreement, which calls on Tehran not to conduct nuclear missile tests for eight years.

Officials said in February the pending Simorgh launch was being watched closely.

A State Department official said at the time that any launch of long-range missiles or space launchers by Iran would be raised in nuclear consultative meetings.

Recent Iranian ballistic missile tests prompted U.N. diplomats from the United States, Britain, France, and Germany to write in March that the launches defied U.N. Security Council Resolution 2231 prohibiting Iran from conducting launches of nuclear-capable missiles.

President Obama, during a recent television interview, defended the Iran nuclear agreement despite the apparent missile launches.

"We are continually concerned about the ballistic missile tests and other military actions that they may take," Obama said on PBS. "But the fact that there is that argument and that there is a channel between the United States and Iran for the first time since 1979, I think that is significant. It provides a possibility of additional changes in behavior."

The launch failure in Iran followed a failed launch of a North Korean intermediate-range ballistic missile last week.

However, in February North Korea conducted a satellite launch that the U.S. Strategic Command described as a long-range missile test.