The Iraqi government said today that Deputy Prime Minister Tareq, Aziz, one of President Saddam's Hussein's most trusted party collaborators, has gone to Moscow for the second time since the war with Iran began in September.

Aziz's visit, which the Soviet Union termed simply a "working visit," reinforced diplomatic speculation here that Baghdad is becoming increasingly disenchanted and concered with Moscow's careful official neutrality in the Persian Gulf conflict and is pressing for more arms.

Not only is Moscow the chief supplier of Iraq's 242,000-strong armed forces, but it is closely bound to Baghdad by a 20-year treaty of friendship and cooperation signed in 1972. One article of the treaty specifics that the two countries will consult and coordinate their positions in the face of any threat to their security.

With the Iraqi Army expending vast amounts of artillery shells, bombs, ammunition and vehicles in its slow moving and increasingly stalemated campaign in Iran's oil-rich Khuzestan Province, Western defense experts here have considered it only a matter of time before its supplies begin to run down, despite official insistence that plenty were amassed for a long campaign.

So far, Moscow has sent Iraq no military supplies beyond what was previously in the pipeline, according to Western intelligence sources. Indeed, Moscow has maintained that it is "neutral" in the conflict with Iran, whose instability and strategic importance it clearly would like to exploit.

Newspaper reports in neighboring Kuwait said Aziz is seeking more military supplies from Moscow, but there was no confirmation of this in Baghdad. He also recently visited France, Iraq's other major arms supplier, in what was interpreted as an effort to secure an arms flow adequate for a conflict most Iraqis expect to endure into the winter.

The fact that in Tehran today the Supreme Defense Council agreed to accept an envoy from U.N. Secretary General Kurt Waldheim was noted here but did not raise any firm expectations of shortening the war. Analysts recalled that the envoy was accepted not as a peace mediator but only to hear Iran's case and to explore "Iraqi aggression."

Those are the same conditions under which Tehran has previously received peace envoys from the 40-nation Islamic Conference and the nonaligned bloc at the United Nations.

Each of those previous missions has foundered on Iran's insistence that it will refuse negotiations with Iraq or even accept a cease-fire so long as Iraqi troops are on Iranian soil. Some observers found encouragement, however, in today's declaration by Hojatoleslam Mohammed Ali Khamenei in Tehran that Iran is seeking clarification of some parts of a five-point plan advanced last month by Cuban Foreign Minister Isidoro Malmierca for the nonaligned nations.

Moscow's ambiguity toward its old ally in Baghdad -- long considered its most important political friend in the Middle East -- was underlined last month when it signed a friendship treaty with neighboring Syria, Baghdad's most implaceable Arab rival in the Middle East next to Iran.

Saddam Hussein himself has repeatedly sought to brush off public suggestions that his relations with Moscow are growing strained because of its stand in the gulf war. In a press conference Monday, he was at pains to emphasize that prior to the war with Iran, Iraq had made contingency plans for a long war and had stocked up with all the arms, spare parts and ammunition that it would need for such a campaign.

Hussein specifically listed the Soviet Union as one of the countries that Iraq feels it has good relations with and said that it is still considered among its friends. Hussein also denied that he expected the Soviet Union to do more for Iraq.

But despite those comments, Iraqi officials in private have expressed concern and even worry about Moscow's lack of support.

Defense analysts here insist that whatever stockpiles of ammunition and spares that Iraq laid down in the past year in which it was preparing for war with Iran, the rate at which Iraq's armed forces have expended ammunition -- expecially artillery shells and antiaircraft missiles -- during their two-month siege of Khuzestan Province's major cities means they are bound to have drawn down stock severely.

The prospect acknowledged, even vowed, by Saddam Hussein that the war will continue into the winter months if not beyond seems likely to force Iraq to seek new supplies. With most of its army supplied with Soviet weapons, Moscow remains the only place it can get new stocks in the quantities that a long, drawn-out struggle will demand.