Brussels — Iran's ruling mullahs see their long-awaited ''big push'' into Iraq as decisive. ''It's time to win or be defeated,'' remarked a young Iranian Islamic militant recently.
The Iranian authorities echo this final-test-of-strength theme. They are determined to topple Iraqi leader Saddam Hussein. Back in late January, Ayatollah Khomeini's heir apparent, Ayatollah Hossein Montazeri, publicly asked the armed forces to launch what he called the ''final assault against Saddam's shaky regime.'' His call was repeated by high-ranking clergymen.
Hence, say well-informed sources contacted by telephone in Tehran, a failure in the present offensive would deal a serious blow to the prestige of Iran's leadership. They say that this means that Iran is ready to raise the stakes to a very high level to achieve its goals.
The Iranian authorities are emphatic, for instance, that they will block the Strait of Hormuz if their oil terminals on Kharg Island are destroyed. ''This is no joke. We will stick to our words,'' an Iranian diplomat said Wednesday in Brussels.
The Iranian offensive was well prepared. Hundreds of thousands of men have been massed along the border. And after last week's initial assaults, Iran said Thursday that its forces had launched a ''sudden blitz.'' Meanwhile, newspapers have published lists of barracks where volunteers can enroll and receive military training.
Radio has interspersed revolutionary songs and military marches with communiques from the front and messages in Arabic exhorting Iraqi soldiers to turn their guns against their officers.
Television has aired numerous programs showing crowds greeting Revolutionary Guards and regular soldiers departing to the front. Every village has sent its own contingent. The city of Tehran has dispatched a hundred bus drivers to transport soldiers to the battlefields.
Officers from the regular Army are said to have been cool initially about the mullahs' proposed offensive. But they eventually agreed to participate after intense pressure from political leaders.
Ayatollah Khomeini himself authorized the armed forces to use long-range artillery to shell Iraqi residential areas. Iraq has been attacking Iranian civilian neighborhoods since the beginning of the war. One week after the launching of the offensive, its results are still unclear.
Iraq said on Tuesday that the invading forces had been wiped out and that thousands of Iranian soldiers had either been killed or taken prisoner.
An Iranian source contacted in Tehran described the situation on the battlefield as follows: During the first hours of the fighting the Iranian troops crossed the wide marshy area lying north of the Iraqi city of Basra and west of the Iran-Iraq border. They then advanced in a flat desert and reached the east bank of the Tigris River.
Iranian soldiers are deployed along the 25-mile stretch between the Iraqi towns of Uzayr and Qurnah. No major Iraqi town has been seized by the Iranians, but at least two bridges on the Tigris are under Iranian control.
A short segment of the Baghdad-Basra Highway, which runs along the west bank of the Tigris, is occupied by Iranian Revolutionary Guards. In a separate thrust , Iranian forces entered the Hawizah marsh southwest of the Iranian town of Bostan. After fierce fighting they occupied the two Majnoon Islands with their 50 oil wells, which Iraq acknowledged. Iranian occupation of these islands could deal a devastating blow to the Iraqi economy.
The Iranians say they are digging in along the Tigris River and are preparing for the second phase of the offensive that should enable them to besiege the Iraqi 3rd Army Corps stationed near Basra.
A source close to the Iranian Ministry of Foreign Affairs said Iranian authorities and foreign diplomats in Tehran were studying new formulas to put an end to the war. Under one proposal, Saddam Hussein would resign as President and be replaced after a substantial shakeup within the ruling Baath Party.
In return Iran would accept a cease-fire and abandon its goal of destroying the Iraqi regime and replacing it with an Islamic republic. Meanwhile, the speaker of Iran's parliament, Hojatolislam Hashemi Rafsanjani, repeated Tuesday in a televised interview that Iran wanted President Hussein to be put on trial.
Iranian diplomats in Europe appear confident about the war's outcome. ''Saddam will fall but the international support prolongs his agony,'' they say.
At the same time the Iranians are stepping up their verbal attacks on the United States. ''From now on the international community should hold the US responsible for what might happen in the Persian Gulf,'' they say.
Referring to the pullout of the US Marines from Lebanon, a Radio Tehran commentator said Tuesday that US soldiers were cowards who had been forced to flee by a handful of Muslim fighters.
''They don't dare face their enemies. All they can do is shell civilian populations from far away,'' the commentator added.
Ayatollah Khomeini, President Ali Khamenei, Hojatolislam Rafsanjani, and Prime Minister Hossein Mussavi recently repeated that the Iranian forces were capable of crushing the Iraqi Army and destroying the Baathists regime.