Iran-Iraq war shifts back to land. Tehran reported not serious in ending war despite limited truce with Iraq

With the oil crisis in the Persian Gulf apparently cooling off, the confrontation between Iran and Iraq is likely to slip back to the marshes around the port of Basra, Western diplomats contacted in Tehran say.

Indeed, those diplomats point out Iran is not seriously looking for a negotiated end to the war - despite the acceptance by both sides of a truce in the shelling of residential neigborhoods and Iran's proposal to extend the truce to the Gulf.

Those diplomats also report that the formidable Iraqi military buildup along the 700-mile battelfield has so far failed to dissuade Iranian political leaders from preparing their ''final offensive.''

A few hours after the United Nations-sponsored truce went into effect, the speaker of the Majlis (parliament), Hojatolislam Hashemi Rafsanjani, repeated that ''Iran would never negotiate with (Iraqi leader) Saddam Hussein.'' Foreign Minister Ali Akbar Velayati said that ''this agreement doesn't change our conditions to bring an end to the war.'' Last Friday at the weekly public prayer ceremony, the faithful shouted ''war, war until victory.'' Moments later, Mr. Rafsanjani announced Iran was ready to stop firing at shipping in the Gulf if Iraq did the same. But this proposal was quickly rejected by Baghdad.

A senior European diplomat in the Iranian capital explained: ''Iran's strategy is aimed at defusing the tension in the Persian Gulf. The Iranians have realized that the Saudis and the Iraqis enjoy overwhelming military superiority in that area.''

A UN-supervised truce in the Gulf would be tantamount to an Iranian victory because it would dash Iraqi hopes to force the Iranians to the negotiating table by disrupting their oil exports.

A Gulf truce would make Iraq's sophisticated Super Etendard aircraft almost useless. ''Don't forget,'' this diplomat continues, ''that a cease-fire in the Gulf would also prevent the Iraqis from carrying out their threats to fire their Soviet-made missiles at oil facilities on Kharg Island.''

This diplomat thinks that for similar reasons the Iranians are eager to have UN observers verify that both sides are refraining from striking at civilian areas. ''The Soviet-made Frog and SCUD missiles have had devastating effects on many houses in Iranian border towns. Iranian retaliations with long-range artillery or classic dropping of bombs have been less effective. Tehran also wants to prevent Baghdad from using cluster bombs against civilian areas in response to its planned land offensive,'' says the diplomat.

Meanwhile, rumors of dissension between the clergy and regular Army officers continue to circulate in Tehran. While clergy leaders have renewed their calls for a ''decisive battle,'' high-ranking Army officers refrain from making statements.

The commander-in-chief of the armed forces, Gen. Qassem Ali Zahirnejad, is said to dislike Revolutionary Guards and volunteers. He apparently believes that the coming operation should be directed by regular Army officers. His subordinate, Col. Sayad Shirazi, who heads the ground forces and is a staunch supporter of the Islamic Republic, is said to have better relations with the Revolutionary Guards' commanders.

An example of how some military men disapprove of the present conduct of the war came Friday when nine Iranians defected aboard a F27 Fokker Friendship aircraft. At least five of the defectors were Army men.

Supporters of the regime contacted in Tehran insist there still exists ''anger of the Iranian population toward the Iraqi Baathist regime after the latest round of shelling of residential areas.'' They say the bombardment on June 5 of the Kurdish town of Baneh left more than 300 civilians dead.

Last Friday, Iranian television aired a report on 4,000 volunteers departing to the front from the province of Gilan. Similiar ceremonies are said to take place regularly thoughout the country.

At sea, no Iranian ships have been attacked for more than a week. Despite the official blockade of the Kharg Island oil terminal, Iranian oil exports are almost back to normal, report oil executives in Europe.

''The national Iranian oil company is offering discounts of up to $2.50 per barrel to compensate for higher insurance premiums,'' one oil company spokesman says. ''No major oil company obtains oil at Kharg but independent dealers do.''

Diplomats who have visited the island in the past say its oil installations are no easy targets. Most pipes run underground. Oil can be loaded into tankers by gravity, which means there are no pumps to blast. Iranian technicians are said to keep storage tankers relatively empty.

Last week's Iranian request to have UN observers in Tehran is the first of its type since the outbreak of the war. In February this year, the Iranians turned down an Iraqi request for an international supervision of a first truce in the shelling of residential areas.

The Iranian government has often reproached the United Nations for not paying enough attention to its grievances. It has so far rejected all Security Council resolutions calling for a cease-fire.

Claude van England reports on Iran from his base in Brussels.