A key field commander in the Iraqi counterattack against Iranian troops holding the southern tip of Iraq's Faw Peninsula on the Persian Gulf today backed off earlier predictions of a quick victory, admitting that the waterlogged terrain of salt marshes and flooded plains made for "slow and difficult going."

Lt. Gen. Maher Abdel Rashid, commander of Iraq's 3rd Army Corps, told reporters visiting his field headquarters 30 miles south of here that he was no longer prepared to predict when his troops would retake Faw, the oil terminal town that Iran captured in a surprise amphibious assault Feb. 9. Rashid was pulled off his normal front north of this port city last week to lead one of three counterattacking Iraqi columns moving toward Faw.

Rashid said, though, that he remained sanguine about an ultimate, and total, Iraqi victory. "Either we will liberate Faw or we will all die as martyrs," he said, as the boom of artillery fire aimed at Iran across the Shatt al Arab waterway to the east could be heard from outside the sandbagged staff headquarters.

"The important thing is not how much land the enemy still holds or how far our forces are from Faw," Rashid said. "The most important thing is that I have already freed a part of my land and destroyed many of the enemy."

In a similiar press conference with other foreign journalists here Saturday, Rashid had predicted confidently that Iraq would retake Faw in "a few days" and that his forces were already within two or three miles of the extensively rubbled town that before the war began in 1980 was Iraq's main oil shipping terminal.

Today, Rashid hedged on those earlier predictions. He refused to say how far his forces were from Faw or to make any new predictions about how long it might take to recapture it.

Rashid said that before the Iranians could be pushed out of Faw, their positions north of the town would have to be destroyed and their supply line -- bringing men and ammunition by boat and pontoon bridge from Iran across the Shatt al Arab -- would have to be interrupted.

Since Iranian shelling began in the first weeks of the war, Faw has been virtually abandoned by its former residents. Until Iran's amphibious and helicopter-borne assault two weeks ago, it was occupied only by troops from Iraq's 7th Army Corps, which was badly mauled in the attack and has had to be reinforced by troops from Baghdad and some of Rashid's for the counterattack.

Western intelligence sources, basing their estimates on satellite photos of the battle zone, said Iran has put about 30,000 troops into Faw this month. That estimate was not disputed by Rashid today. He claimed that the Iranians had been putting "a division a night" across the bridge. A division normally totals about 10,000 men.

Rashid indicated that aside from the difficulties of the waterlogged terrain and vagaries of weather, one reason Faw would not be recaptured as quickly as he had previously hoped was that the Iraqi Army was hoping to avoid storming the well-entrenched Iranian positions with infantry. Iraq has sought to minimize its casualties throughout the 5 1/2-year-old war against more populous Iran.

Rashid's column is inching down the peninsula's recently built central military road. Another column has been all but stopped along the main Basra-Faw road that parallels the Shatt al Arab and is in range of Iranian artillery all the way.

A third column has been moving with some apparent success along a western dirt road from the Iraqi naval base at Umm Qasr on the Khor Abdallah waterway, across from Kuwait.

Rashid, considered one of the most effective Iraqi commanders, said that once Iraq's superior firepower -- in artillery and air support -- crushes the Iranians' positions north of Faw and cuts their supply line, "they will have to surrender," without Iraqi troops having to engage them in hand-to-hand fighting.

That is a notion not shared by western military observers, who say that the past fanaticism of Iran's Revolutionary Guards and soldiers indicates that they fight until death rather than surrender or run, because of their religious beliefs that if they fall in battle for God, they are guaranteed entry into paradise.