Iraqi military forces are beginning to learn how to operate sophisticated U.S. Hawk antiaircraft missiles and radars that were captured in Kuwait and brought back to the Baghdad area, U.S. officials and government analysts disclosed last week.

The development has aroused concern because the Iraqis captured about 150 of the highly accurate missiles, which, in the hands of properly trained military technicians, could pose a substantial threat to U.S. and allied warplanes if they attacked Iraqi military targets.

Many U.S. and allied military aircraft in the region have no ready means of protection against the Hawk system, the officials said.

They said U.S. concerns stemming from the initial Aug. 2 capture of the Hawks were intensified last week, when electronic intelligence operations in the region detected the first characteristic signs of Hawk radar operation at a special test site for air-defense equipment near Baghdad.

The radar emanations indicated that Iraq is "playing around" with the weapon systems, as one official put it, but still remains weeks to months away from actually deploying them.

While U.S. officials two weeks ago had publicly dismissed any possibility that the Iraqis could operate the complex weapons, a senior U.S. analyst who asked not to be identified said last week that "in a while, the Iraqis will know how" to use them and that many U.S. aircraft are not equipped to defeat the systems.

A U.S. official familiar with military intelligence agreed and said the development "will complicate our planning if we actually go after Baghdad -- and the more complex the operation, the more likely we are to suffer losses." A senior defense official said a classified report of the Iraqi action was swiftly circulated to policy-makers last week because the Hawk "is a damn good system, and we would not like to see the Iraqis operate it."

One official said Iraq had evidently captured four or five Hawk "batteries," mobile installations each containing six missile-launchers, that Kuwait bought from the United States to provide a comprehensive air defense of its northern territory. Each missile is designed to strike a high-speed military aircraft flying at low-to-medium altitudes up to 25 miles away.

The missiles, whose name is the acronym of Homing All the Way Killers, are said to be superior to any other antiaircraft weapon in the Iraqi arsenal and identical to the best equipment now possessed by Saudi Arabia. An industry source said the version captured by Iraq was specifically improved in the mid-1980s to avoid defeat by modern electronic countermeasures.

Although the missiles, launchers and associated radars have previously been provided by the United States to friendly nations in Europe and the Middle East, Defense Department officials have repeatedly barred sales to hostile powers and said they never anticipated they would be operated by Iraq.

"We typically do not have any protection against Hawk missiles," said Air Force Chief of Staff Michael J. Dugan in interviews shortly before his dismissal Sept. 17 by Defense Secretary Richard B. Cheney.

Another senior Air Force official said tactical air commanders are "not worried now" because the Hawk systems captured by Iraq are still being tested. This official, who asked not to be identified, said that even if the systems become operational, "we feel we can deal with them" through a combination of radar jamming and evasive aircraft maneuvers. "We know that system cold," the official said.

But other officials said Washington has been so concerned about the missiles' potential use against U.S. warplanes that senior Jordanian officials were asked about Israeli reports that Jordanian technicians were teaching the Iraqis how to use them. Jordan possesses more than 100 Hawk missiles purchased from the United States.

"We have assurances from the highest levels of the Jordanian government that . . . {the training} is not happening, and we don't have any collateral information that would lead us to question those assurances," Undersecretary of State Reginald Bartholomew told the Senate Foreign Relations Committee on Oct. 4.

"We've been looking very carefully at those missiles for obvious reasons," Undersecretary of Defense Paul Wolfowitz told the same hearing. But he added that available evidence indicated that "you can't . . . operate a sophisticated system like a Hawk missile without American technicians."

Other officials privately disputed this assertion, noting that Iraq has gained extensive experience operating modern, but less sophisticated, Soviet and French-made antiaircraft systems, some of which were used in Iraq's eight-year war with Iran. "It's all basically the same stuff, operating by the same principles," one official said. "It's only a matter of figuring out what connects to what."

Another official, noting Iraqi proficiency with other modern equipment purchased from the West, said "it's not like the missiles were captured" by a technologically backward country.

One U.S. analyst speculated that Iraqi technicians could be trained by retired Jordanian military officials acting outside official channels, by Kuwaiti prisoners of war or by Palestinians formerly employed by the Kuwaiti military.

Each of the Hawk batteries now in Iraqi hands includes mobile missile-launchers, three types of radar, a powerful optical sensor and multiple trucks and trailers packed with computers, sensors and communications gear. The missile guidance systems incorporate what Jane's Weapon Systems in 1988 called the latest "state-of-the-art" equipment. Since then, an improved version has been developed for deployment with U.S. forces.

Independent experts said the weapon system has proven its effectiveness in combat, including the 1973 Arab-Israeli war, when more than 20 Soviet-built MiG aircraft were downed by Israeli-owned Hawk missiles that are less sophisticated than those in Iraqi hands.

Iran used Hawk missile systems obtained from the United States before the Islamic revolution in 1979 to defend key military installations from Iraqi attack during the conflict that ended in 1988. A specially modified Israeli Hawk system intercepted a high-flying MiG-25 reconnaissance aircraft over Lebanon in 1982. And a French-owned Hawk missile shot down a Libyan Tu-22 supersonic bomber over the capital of Chad in 1987.

Some U.S. legislators have cited Iraq's capture of the Hawk system in arguing against additional arms sales to the region, such as the planned $21 billion, two-step sale of tanks, aircraft and other weapons to Saudi Arabia.

"We have a very unfortunate history of making the most sophisticated deliveries to governments which, although they appear stable at the moment, prove to be unstable," said Rep. Tom Lantos (D-Calif.), who said he favors leasing -- not selling -- new arms to friendly nations in the region.

Officials said Iraq also captured from Kuwait, and evidently is trying to learn how to operate, several thousand U.S. TOW antitank missiles, some self-propelled 155mm howitzers, AIM-9H air-to-air missiles and 16 A-4 attack aircraft.

Staff researcher Cathy Wall contributed to this report.