Iraqi tanks and troops broke through Iranian defenses in the port of Khorramsbahr today in preparation for a concerted attack on the nearby oil refining center of Abadan, Iraqi authorities reported.

The Iraqi push came amid signs that the Persian Gulf war, now in its 20th day, is splitting the Arab world into pro-Iraqi and pro-Iranian camps, with each side warning the other states not to support its adversary.

The official Radio Baghdad, announcing a "great victory," said its forces crossed a pontoon bridge across Iran's Karun River south of Khorramshahr and dealt Iran "direct and punishing blows." Iraq also claimed to have blown up Iranian oil pipelines between Khorramshahr and the provincial capital of Ahwaz, the administrative center of Iran's oil industry.

Earlier, Iraq announced a break in diplomatic relations with North Korea, Libya and neighboring Syria, accusing the three countries of sending weapons to Iran. The Iraqi Foreign Ministry charged that its fellow Arab states, Syria and Libya, "have collaborated with the Persian aggressors, providing them with weapons and ammunition through an air bridge connecting Terhan with Damascus and Tripoli."

In Tehran, President Abol Hassan Bani-Sadr told a French interviewer that if any Arab states on the Persian Gulf came to Iraq's aid, the Iranian Air Force would attact their oil facilities.

"We have the means to make them understand we won't spare anyone," Bani-Sadr told the French news magazine, Le Nouvel Observateur. "If the gulf countries enter the war, we will destroy their petroleum installations."

He added, "We would also attack the Strait of Hormuz if the war worsened and if the big powers got involved indirectly through other countries."

The magazine also quoted Bani-Sadr as saying he was willing to negotiate some of the territorial disputes between the neighboring OPEC nations, but "not on the Shatt-al-Arab," the vital waterway dividing the two countries in the south and providing access to Iran's biggest cargo port at Khorramshahr.

"The two countries each have the right of free navigation," the Iranian president said, "But one can discuss the some hundreds of square kilometers that the Iraqis claim on the side of Ilam."

He was referring to a narrow strip of territory in Ilam Province that Iraq claims should have been ceded to it under a 1975 treaty. Bani-Sadr's reported remarks marked the first time that Iran has expressed willingness to negotiate with Iraq, but fell far short of meeting Iraqi demands that the disputed Shatt-al-Arab channel be entirely under Iraqi control.

Bani-Sadr's warning to Arab states came as Jordan's King Hussein, the most vocal supporter of Iraq in the war, traveled to Saudi Arabia in an apparent effort to enlist open Saudi backing for Baghdad. The king's support for Iraq apparently has alienated Moscow, which is trying to walk a fine line between the two warring neighbors. The official Soviet news agency Tass announced that a trip to Moscow by Hussein, which had been scheduled for next week was called off by "mutual agreement."

With Iranian and Iraqi oil exports still shut off by the fighting, Saudi Arabia, Qatar, Kuwait and the United Arab Emirates agreed to raise their combined oil production by 1 million barrels a day to help offset any world oil shortfall, Venezuelan Energy Minister Humberto Calderon Berti told reporters in Caracas, according to news services.

He said the agreement was reached by the four countries' oil ministers at a meeting in Taif, Saudi Arabia yesterday. Although combined Iranian and Iraqi oil exports amounted to about 3.5 million barrels a day before the war, about 2.5 million barrels a day were flowing into stocks. The new production increase, therefore, should cover any oil shortfall for the time being.

The agreement came as the Persian Gulf war continued to inflict damage on oil facilities.

Military communiques issued in Baghdad said Iraqi warplanes again bombed Iran's main oil export terminal at Kharg Island in the Persian Gulf. Baghdad said Iranian warplanes killed four civilians in a raid on southern Iraq and that Iraqi forces retaliated by hitting a factory in Ahwaz and setting it on fire.

Unofficial sources in Basra said Iraqi Army armored units crossed the Karun River after subduing tenacious resistance in Khorramshahr by Iranian regular troops and Revolutionary Guards, who have been holding out for more than two weeks.

The crossing, described by Baghdad Radio as its armed forces' biggest amphibious operation, followed an intensive Iraqi artillery barrage, the sources said.

In the last two days the highways between Nasiriya and Basra have been crowded with convoys of Iraqi troops, tank carriers and artillery for an expected assault on Iran. However, there was no indication here tonight that the Iraqis had begun an attack on the ground against Abadan.

Meanwhile, about three dozen Iranians prisoners of war, apparently captured in today's river crossing, were paraded through the streets of Basra as hundreds of Iraqi civilians cheered and ran after the motorcade.

The prisoners sat in two bright orange dump trucks heavily guarded by Iraqi soldiers with a long stick occasionally poked at the grim-faced prisoners as the crowd shouted "Death to the Persians."

Some Iraqi troops fired hundreds of rounds from automatic rifles as the convoy wound its way through the city.

Iraqi authorities in Baghdad claimed that 50 Iranian soldiers were killed and four Phantom fighter-bombers shot down in the day's fighting. A communique said that 536 soldiers and 20 Revolutionary Guards had been taken prisoner. The official Iraqi News Agency quoted a captured Iranian officer as saying that more than 1,000 Iranians had been killed in Khorramshahr and Abadan.

The Iraqi command admitted two soldiers killed and 11 wounded in today's fighting, in which it said two Iraqi tanks and two military vehicles were also destroyed.