Iraq appeared yesterday to be on the verge of finally seizing control of the besieged Shatt-al-Arab port of Khorramshahr and said it was battling for three other cities in Iran's oil heartland of Khuzestan, including the provincial capital of Ahwaz. But Iran denied the Iraqi claims and said it was still holding on at all four points.

In Baghdad, President Saddam Hussein declared that Iraq had scored a "glorious victory against the oppressor clique in Tehran" and was now ready for a cease-fire and negotiations to settle its dispute with Iran. Iraq, he said, would negotiate "directly" or through any third party or international organization "in which we have confidence in achieving a just and honorable solution safeguarding our rights."

At the same time, Iraqi Foreign Minister Saadoun Hammadi said his government was taking every measure possible to restore its war-disrupted oil exports and he asked other producers to step up production to compensate for the loss of Iraq's 3 million barrel-a-day production. But he denied reports that all of the country's exports had been halted.

"There has been damage, there has been a decrease in our oil exports, but our exports have not fallen to zero," he told a press conference in Baghdad for Western correspondents.

Meanwhile, international pressure continued to mount for an end to the fighting, although there was no indicatin that Iran was ready to heed such appeals. At the United Nations, the Security Council unanimously adopted a resolution last night calling on Iran and Iraq to stop their war and accept mediation to settle their differences.

In Tehran, however, President Mohammed Zia ul-IIaq of Pakistan ended the first leg of his peace mission on behalf of the 40-member Islamic Conference, reporting after several meetings with Iranian President Abol Hassan Bani-Sadr that Iran was still in "a revolutionary stage" when "conciliation and mediation do not work."

An aide to Bani-Sadr was quoted as saying that Zia had "achieved nothing" and that "while it was nice of him to come, we are going to fight on until the last Iraqi soldier is off Iranian soil."

As the war dragged on through its seventh day, Iraq claimed it had captured Ahwaz, 50 miles inside Iran's southwestern, oil-rich province but Iran described the Iraqi claim as a "great lie" and asserted that victory was near.

"Crush the enemy, use all possible means," the Iranian joint chiefs of staff said in a message to all Iranian soldiers. "The moment of victory is near, nearer than you think."

Residents of Ahwaz, a city of more than 300,000 people, contacted by telephone by the Reuter news agency bureau in Tehran denied that there were any Iraqi forces there and said the provincial capital was quiet after an intensive Iraqi shelling Saturday in which at least 29 persons were reported killed and 119 others injured.

Ahwaz is located in the center of Iran's vital oil fields, and its fall would signal a major Iraqi victory in a province the Iraqis call "Arabistan" and to which they have laid claim in the past because of its large Arab minority. So far, Iraq has given no indication that the seizure of Khuzestan, as the Iranians call the same region, is among its war objectives. k

There was some independent confirmation yesterday that Iraqi claims to have taken the Shatt-al-Arab port of Khorramshahr were close to coming true. Several news agency correspondents taken to the outskirts of the city reported that Iraqi forces, which had first laid siege to the port city a week ago, had now all but taken it.

United Press International correspondent Joseph A. Reaves, reporting from 500 yards outside the city, said that practically all Iranian forces had abandoned Khorramshahr and that Iraqi commanders said that only a handful of snipers and some fanatic Revolutionary Guards were still holding out.

Reaves also reported that some ethnic Arabs living in Khuzestan had joined regular Iraqi forces in the fighting both for Khorramshahr and nearby Abadan, where Iran's giant refinery, one of the world's largest, has been ablaze for the past week.

Although Iraq has repeatedly claimed that Abadan was also on the point of falling, reports from the area indicated that the Iranians were still in control and putting up a spirited defense of that city.

The fourth Khuzestan city Iraq has set its sights on capturing is Dezful, 70 miles directly north of Ahwaz. Baghdad said its forces had successfully crossed the Iranian defense line along the Karkheh River and that "the town is doomed."

There was no independent confirmation of this report, however, as Iraqi authorities were not allowing Western reporters to visit any other front-line locations than Khorramshahr.

In other war action, Iraq reported that Iranian warplanes had attacked several towns and sites, including Mosul in the north and the oil refinery at Basra once again. It said that only light damage was inflicted by the bombings and that 11 more Iranian jets were shot down, three of them in fierce fighting at Dezful.

Iraq now claims to have down 813 Iranian planes, a figure which, if accurate, would mean that the country's still functioning Air Force would have been virtually wiped out. Reports indicated, however, that was now flying many fewer sorties than earlier in the week, although it is not clear whethers this is because of a lack of planes now or of fuel to fly those still serviceable.

Meanwhile, Iranian war communiques reported Iran's warplanes and helicopter gunships had destroyed or damaged 86 Iraqi tanks in the last 24 hours. They also said Iraqi jets had again raided Kharg Island, where the country's main oil terminus is located, and that four of them had been shot down.

For the first time, the Iranian military command admitted indirectly that the border town of Qasr-e-Shirin had fallen and that Iraqi forces were moving toward another town 30 miles to the southeast. The joint chiefs of staff said an Iraqi ammunition dump in Qasr-e-Shirin was blown up by Iranian forces and an Iraqi armored column heading toward Gilan-e-Gharb was attacked.

Despite mounting evidence that Iran's front-line defenses were increasingly hard pressed, Iranian officials were reported in an optismistic mood yesterday.

Reuter quoted one of them as saying Iraq had done Iran "a great favor" by invading the country, "Before that, nobody knew exactly how the armed forces would react. But the past weeks has proven that they have conviction in defending Iran," he said. "The performance of our Air Force astonished everyone, even us. Who would have believed that within 24 hours after the first Iraqi planes attacked we could have 140 fighters in the air?"