BAGHDAD, IRAQ -- After two devastating winter offensives that have given Iran the momentum in the Persian Gulf war, Iraq has fielded a new defensive strategy that accepts the loss of control over much of its border areas and concentrates on protecting its eastern cities and oilfields with a heavily fortified garrison army standing watch behind ramparts of earth and concrete.

Western diplomats, military analysts and Iraqi officials interviewed here said this new strategy has emerged since Iraq's military leadership has learned the futility of its own offensive campaigns. Instead, it has sought a military posture that "contains" Iranian military thrusts while promoting a negotiated settlement in the United Nations of the seven-year-old war.

These analysts asserted that Iraq, whose debt-ridden economy is beginning to rebound, can prevent any significant Iranian military gains for the foreseeable future. Even with Iran's 49 million population pitted against Iraq's 16 million, these officials said, Iraq, with its heavy conscription program, unrelenting pursuit of deserters and access to the latest western weaponry will continue to field a military machine that Iran is unlikely to overpower.

Western officials still express concern about possible unexpected developments, such as Iran's sudden breakthrough onto Iraq's Faw Peninsula in February 1986. But barring a major collapse, these officials said, Iraq should be able to protect its war-strained society for years to come behind a formidable north-south defensive barrier.

"If you want to be gross about it," one western official said, "there have been 150,000 Iraqis killed since the beginning of the war. But this year, 190,000 Iraqi boys will reach the age of 18."

This inherent manpower strength in the smaller of the two countries, where the state pays bonuses for large families, is visible on this year's battlefield in southern Iraq. A major offensive against Basra, Iraq's second-largest city, had been predicted there by a number of analysts.

An assault against Basra's outer defenses last winter brought Iranian artillery within range of the city's 1 million residents. Weeks of heavy shelling drove hundreds of thousands of them to refuge outside the city.

Since then, however, Iraq has refortified Basra's defenses, replacing sandbagged and earthen berms with reinforced concrete bunkers and pillboxes.

This year, nature has provided an additional defense. The Tigris River, which feeds the Shatt al Arab waterway, Basra's final barrier to an Iranian attack, is running at record-high levels.

In manpower, Iraq's southern flank is protected this winter by four armored divisions totaling 100,000 infantry soldiers, according to western sources. "There are simply more Iraqi troops in the south than there are Iranians on the other side," one western diplomat said.

Another western official added, "The Iranians don't have the cannon fodder for a major offensive this year." This official said last year's call by Ayatollah Ruhollah Khomeini for 100,000 volunteers produced 80,000 young Iranians who were thrown into the Basra campaign. "This year they only got 40,000 and you need 100,000 men for the kind of meat grinder they are facing this year -- more if you hope to achieve something you can call a victory," he said.

In the only significant fighting this year along the 700-mile frontier, Iran appears to have seized 50 square miles of mountainous territory near Mawat, northeast of Kirkuk, center of Iraq's largest oil fields.

One western military analyst said Iraq has "enough manpower and artillery up there to contain the Iranians."

This official said Iraq has mounted some counteroffensives in a campaign that began Jan. 15, but these appeared aimed largely at protecting Sulamanieh, a nearby provincial center.

"I think the Iraqis don't care about the mountains," he said, adding, "They would just as soon let the Iranians operate there and they wouldn't be fighting around Mawat if they didn't have to protect Sulamanieh."

The last Iraqi offensive occurred in May 1986 when Iraqi infantry and armor drove across the Iranian border east of Baghdad and seized Mehran. At the time, Iraqi President Saddam Hussein said he would hold Mehran until Iran agreed to a peaceful settlement of the war. But after weeks of intensive counterstrikes by Iranian forces, the Iraqi column was forced to withdraw.

This year, an Iraqi offensive seems all but inconceivable as the Baghdad regime works tirelessly with Arab leaders in support of a U.N.-sponsored cease-fire call that now awaits a consensus in the Security Council for a vote to impose an international arms embargo on Iran.

"This kind of stalemate could drag on for a very long time," said a European ambassador.

In the meantime, Iraq has launched economic reforms and construction projects that are intended to build relative prosperity while the garrison military forces keep the war at a distance.

"Saddam is going capitalist," one western diplomat quipped, by unshackling many of the traditional restraints to private investment. "They are selling off state agricultural properties and industries, breaking down bureaucracy and increasing production incentives," the diplomat said.

The result has been an increase in imported goods that had all but vanished from Iraqi stores, although prices have increased.

Iraq's oil exports, which account for 90 percent of its foreign earnings, have climbed to nearly 3 million barrels a day, just below its prewar level. New pipelines have almost replaced the export routes Iraq lost when Iran closed its only southern port and Syria shut down a major overland export line to the Mediterranean.

Together, these factors suggest a continuing Iraqi resilience, officials here said. Still, U.S. Ambassador David Newton has suggested to colleagues in the diplomatic corps that the greatest threat to Iraq is the "brittleness" of its society, which has lived under a harsh regime both before and since the war began.