WASHINGTON (AP) _ Still suffering from its resounding defeat in 1991, Iraq's military nevertheless has been reconstituted into a substantial and threatening force, U.S. intelligence estimates and outside experts say.

The military that President Clinton hit with a limited cruise missile strike last Tuesday is about 40 percent of what Iraq fielded against President Bush and an international coalition in the Persian Gulf War.

Yet Iraq remains a potent military power, capable of quickly moving forces into menacing proximity to Kuwait, as it did in 1994, and of attacking the Iraqi Kurdish population, as it did immediately after the Gulf War and again this month.

``Desert Shield and Desert Storm was not as devastating a blow as everyone thought it was,'' said Paul Beaver, editor of Jane's annual Gulf States Security Assessment. ``Very few of the elite Republican Guard forces were affected by the Storm. That meant that basically the professional core of the armed forces was left intact.''

In some ways, the Gulf War may have weeded out weaker elements of the Iraqi military, and the force might even stand further cuts. A detailed study of Iraqi strength by Anthony Cordesman of the Center for Strategic and International Studies indicates that Iraq may be maintaining too large a force structure to allow its military to recover and rebuild.

Weapons and manpower remain at about the same levels as immediately after the Gulf War, according to London's International Institute for Strategic Studies, which publishes annual detailed estimates of military strength worldwide.

Across the board, the Iraqi military is smaller _ down 618,000 from a 1990 high of 1 million active-duty forces; down 2,800 main battle tanks from 5,500 in 1990; down 1,500 towed artillery pieces, half the 1990 number; and down 197 fighters and fighter-bombers from 507 in 1990. These figures largely agree with separate analyses conducted by the Pentagon's Defense Intelligence Agency.

In addition to the destruction wrought by the Gulf War, Iraq has chafed under an international embargo on arms imports and oil exports, cutting off easy access to a country that before 1990 bought $2 billion to $3 billion in weapons every year. Iraq has faced pressure as well from the United Nations Special Commission on Iraq to eliminate its weapons of mass destruction.

Through these difficulties, Iraq has carefully maintained the formidable arsenal that survived the Gulf War using a skilled corps of indigenous technicians and engineers. It has also adapted civilian technology such as fiber optics and computers to weapons systems and imported materials through a somewhat porous embargo, according to Middle East experts.

Even at its reduced levels, the Iraqi military fields more modern tanks and operational artillery pieces than any of its neighbors, according to the Center for Strategic and International Studies. It is second in the Gulf region only to Iran in active-duty manpower.

Experts disagree on the effect of the arms embargo.

CSIS's Cordesman concludes that black-market arms imports and local manufactures ``can only provide an erratic and inefficient substitute for large-scale resources.'' At the same time, Cordesman says, ``We never assumed for a moment that we could halt the pace of Iraqi technological development of actual weapons.''

Beaver, the Jane's editor, argues that the border between Iraq and Jordan remained open for two years after the Gulf War and that Baghdad has been able to continue importing military components through the black market since then.

Evidence of this practice emerged last year when Iraq acknowledged to U.N. inspectors that it had imported growth media for biological weapons development. Jordanian authorities also intercepted a $25 million shipment of Russian-made gyroscopes that could be used to guide long-range missiles.

Iraq's efforts to develop nuclear, chemical and biological weapons are a key source of U.S. concern.

Gen. John Shalikashvili, chairman of the Joint Chiefs of Staff, said Sunday on NBC's ``Meet the Press'' that the United Nations has worked vigorously to prevent Iraq from rebuilding its nuclear and conventional weapons programs. Despite that, Shalikashvili said, ``We are not naive enough to say that we now know everything. So everything is possible.''

U.N. inspectors have found evidence of two successful nuclear weapons designs, according to the CSIS. A Pentagon proliferation report notes that Iraq retains facilities necessary to develop biological weapons and could easily shift its civilian chemical plants to military production.

In a report on Iraqi military strength, the U.S. Central Command, which waged the Gulf War, summed up its view of the war's impact on Iraq: ``Despite these problems, Iraq remains one of the most powerful military forces in the region.''