DUBAI, UNITED ARAB EMIRATES, SEPT. 18 -- Iran has shown new flexibility on ending its war with Iraq, but deeply ingrained suspicions may make it difficult to exploit what is seen as a narrow diplomatic opening, according to diplomatic sources familiar with details of United Nations Secretary General Javier Perez de Cuellar's recent mission to the two countries.

Perez de Cuellar, who briefed members of the U.N. Security Council on Wednesday about his trip, is said to have found Iraq highly suspicious of Iran's tactics and unyielding in its demand that Security Council Resolution 598, which calls for a cease-fire and an end to the war, be implemented with no changes.

Iran, as its leaders have said publicly, insists that Iraq be branded as the aggressor in the seven-year-old conflict, but Tehran has shown an unprecedented willingness to discuss details of the Security Council resolution, according to the diplomats.

In a major departure, Tehran is said to have explicitly dropped its earlier demands for the removal of Iraqi President Saddam Hussein as a condition for peace. But the issue of fixing blame for the war is said to be a real one.

"They have a very deep sense of injustice. It is something they feel deeply," according to diplomats familiar with Perez de Cuellar's confidential report.

The Iranian shift is viewed in some quarters as the result of growing weariness with the war, matching Iraq's. The change is tentative, however, and Iraq is said to believe that Tehran is simply trying to buy three or four months to build up strength for another major land offensive.

As a result, Baghdad is expected to escalate the heavy military pressure on Iranian shipping and cities that it demonstrated before and after the secretary general's four-day visit to the region.

Iraqi aircraft bombed Iran's Kharg Island oil terminal and two offshore oilfields today, according to an Iraqi military communique. Iraq later said it also had attacked Iran's Lavan Island oil terminal in the southern gulf and had hit an unidentified tanker off the Iranian coast.

Iran's national news agency, IRNA, said Iranian artillery pounded the southern Iraqi city of Basra again today and thwarted the air attack on Kharg, shooting down an Iraqi Mirage warplane. An Iraqi oil installation also was reported hit.

As fighting on the traditional fronts escalated, IRNA said that Kurdish guerrillas had killed or captured more than 1,000 Iraqi troops in heavy fighting in northwest Iraq near vital Iraqi pipelines that carry much of Baghdad's oil for export.

On the diplomatic front, "There are no makings of a bridge between {Iran and Iraq} right now," according to one diplomat's assessment of Perez de Cuellar's report. "Maybe there is a very small opening."

Iran would appear, at a minimum, to have blunted the Iraqi diplomatic drive that led to passage on July 20 of the U.N. resolution. Diplomats familiar with the behind-the-scenes maneuvering at the United Nations now believe there will not be an immediate push for an arms embargo against Tehran if it fails to comply.

"They may not be too keen to move to an embargo resolution right away," said one diplomat.

The original Security Council resolution demanded an immediate cease-fire, a withdrawal to internationally recognized boundaries, exchange of prisoners and other measures. It also called for an impartial commission to assess responsibility for the conflict.

Tehran told Perez de Cuellar this week it would be willing to abide by an informal cease-fire while the commission does its work, and then would agree to a formal cease-fire "after Iraq is found to be the guilty party," according to diplomats and unofficial copies of the U.N. report obtained by news agencies in New York. Iraq has demanded that the formal cease-fire come first.

The two also are at odds on how the fault-finding process would work. Iraq is said to have insisted that the International Court of Justice, or World Court, decide the issue, while Iran "wants something more expeditious," according to informed diplomats.

"The Iraqis were inflexible, very rigid," according to a diplomat familiar with the mission. "They are very suspicious of the Iranians and feel they are maneuvering and misleading."

That the Iranians have a reputation of "not having been very straightforward" in past negotiations does not help them gain credibility now, said one diplomat with long experience in dealing with Tehran.

Despite the lack of external pressures on Baghdad, other gulf Arab states are anxious to end the war.

"The Saudis and the Kuwaitis would appear to be anxious to bring the fighting to a halt before it spreads into their territory," said a diplomatic source, "but the Saudis may be even more suspicious of the Iranians now after Mecca. They may close ranks with the Kuwaitis."

A confrontation between Saudi police and Iranian pilgrims in Mecca on July 31 left 322 Iranians dead and has led to bitter exchanges between Saudi and Iranian leaders.

The Iranians were depicted this week as having taken a number of new paths in the current round of U.N. negotiations. "There were so many firsts, it is hard to ignore them," said one diplomat.

Whereas Iran previously would reject any discussion of U.N. proposals out of hand, this time Tehran was portrayed as expressing an interest in detailed discussions of each item in the Security Council resolution.

"They discussed the clauses, seriously, one by one," said a diplomat. "But when all was said and done, they made it clear that pressure would not work."