A top Iranian leader pledged today that Iran will continue its winning struggle against Iraq until the government of President Saddam Hussein is overthrown.

Speaking before the Iranian parliament, Hojatoleslam Ali Akbar Hashemi Rafsanjani, its speaker, said his country harbored no territorial ambitions but would not forgo any of its rights, "and our greatest right is the overthrow of Saddam."

Rafsanjani gave no indication how Iran planned to bring down the tough Iraqi leader. Nor did he say whether Tehran planned to send troops across the border into Iraq following the rout of Iraqi forces from the Iranian port city of Khuninshahr on the Shatt-al-Arab waterway Monday.

His speech came as 3,000 Iraqi prisoners of war captured in Khuninshahr arrived in Tehran on three trains, the first of a reported 12,000 taken during the two-day battle for the city.

The official Iranian news agency reported the prisoners were welcomed at a nearby sports stadium and had shouted slogans including "Down with Saddam" and "Death to America."

At a press conference in Tehran, a government spokesman said today that Iran now held slightly more than 40,000 Iraqi prisoners of war as a result of the 20-month war, but did not indicate what Iran planned to do with them.

With Iraqi forces now in full retreat from the southern part of Iran's Khuzestan Province, Iran appears to have virtually won the war to oust the Iraqis from its territory and must decide what action it will take next.

In a tough statement given in an interview with the British Broadcasting Corp. in London, Iranian Oil Minister Mohammed Gharazi said there was "no question of negotiations with the Saddam Hussein regime" for a formal end to the war.

Iran has demanded in the past the total withdrawal of Iraqi troops from Iranian territory, reparations of at least $50 billion and an international committee to determine the aggressor in the war. Recent statements suggest it is now also demanding the removal of Saddam Hussein from power as a condition of peace.

Whether Iran plans to invade Iraq is not known. Most analysts here believe the Iranians will employ other means because of the international repercussions such a move might have.

Instead, they believe Iran will attempt to recruit guerrillas among the 40,000 Iraqi war prisoners and 100,000 other Iraqis largely of Iranian origin and Shiite faith who were expelled from Iraq several years ago by Saddam Hussein's government.

Shiites form a majority of Iraq's 14 million people and they are concentrated in the southern provinces where several Shiite holy sites are located. Observers believe it is likely that the Iranians will find a large number of Shiite volunteers to fight against the Baghdad government.

In addition, the Iranians are also likely to step up assistance to Kurdish dissidents in northern Iraq, where there are reports of sporadic clashes with security forces.

In the war today, Iraq said the Iranians began shelling Iraqi territory and also indicated retreating Iraqi forces were fighting Iranian troops north of Khuninshahr.

Iran reported "sporadic fire" in the central sector of the war front where recently little fighting has been going on, or at least little that has been officially reported.

Iraq still holds land far north into Iran's Kurdistan region. So far as is known, the Iraqis have not yet retreated from those areas, estimated by some sources to include about 3,000 square miles of Iranian territory.

Just how shaken Saddam Hussein's government is by its latest reverses on the battlefield is difficult to assess here.

Kuwaiti analysts note that there have been no reports of any serious political opposition inside the country recently and believe the Iraqi leader retains tight control of both the ruling Arab Baath Socialist Party and the state security apparatus.

But others believe that if the Iranians refuse to negotiate and begin subversive activities, pressure may rapidly develop for his removal to establish peace.

Few here believe Saddam Hussein will give up power easily. But the mood of the armed forces following the latest defeats may prove a decisive factor.Without their support, analysts agree, it is difficult to see how he can survive for long.