The brutal Soviet campaign to intimidate Pakistan escalated two weeks ago when a senior Soviet ministry official bluntly told the Pakistan ambassador in Moscow: "Tell your government that it is making undeclared war on the Soviet Union."

This bully-boy game, as the Russians mire themselves more deeply in their war against the brave Afghan resistance, is designed to force Pakistan to accept the Soviet-imposed Babrak Karmal regime in neighboring Afghanistan. If Pakistan wilts, other Moslem states might follow and ratify Russia's absorption of Afghanistan.

Despite the intimidation and the low estate of Pakistan's military forces, President Zia has a different idea. He made that plain to us in an exclusive interview at the presidential mansion in Rawalpindi.

"We feel compromise is not the answer," Zia told us. "The Soviets have got to be made to believe that what they have done in Afghanistan is not right. They must rectify their position" -- get out of Afghanistan.

The refusal to knuckle under is certain to intensify Soviet military action against Pakistan, however veiled in the guise of "hot pursuit" of Afghan freedom-fighters seeking respite in Pakistan. Soviet intervention in Pakistan, however, will force President Reagan to lead the West into making a stand at long last with something more than a brief and spineless grain embargo against Moscow's march through South Asia.

But having treated Pakistan as a pariah for 15 years, amidst self-serving cries from liberals who managed to end all military aid, the United States finds Pakistan dangerously strapped. An immediate emergency shipment of new weapons is essential for this country to handle any Soviet thrust across the 1,400-mile Afghan border. Such a thrust is predictable as the opening Soviet move, perhaps to destabilize Zia.

Whatever the preliminary objective, Soviet troops on the march in Pakistan would be another humiliation for the United States with this implicit dare: What are you going to do about it?

We asked Zia if Soviet pressure on him in the end might force him to back down and make a deal with Moscow. "They have tried their best," he said. "There has been military pressure. They have knocked out some of our border posts. We have suffered some casualties. They know they can teach Pakistan a lesson. It is the freedom-fighters in Afghanistan that are keeping the Russians engaged."

No, Zia said, Pakistan will not yield to the far greater pressures expected from the Soviets in the near future. He sees only two ways to stop the Soviet march: pressure of world opinion, or arms. "World opinion" includes both the will and power of the West, even though both lag behind the Soviets, and the Islamic world, which includes vast areas lying inside the Soviet Union itself -- Azerbaijan to the West and Uzbekistan, Tajikistan and other Soviet Moslem states along the Soviet-Afghan border.

Deprived of U.S. military aid, Pakistan today is at the bottom of its military barrel. Zia does not want an alliance with the United States, only credit to buy weapons. Earlier alliances, despite direct pledges from at least one president, did nothing for Pakistan during its two losing wars with India (the main Soviet ally in South Asia now acting aloof from Russian killings in Afghanistan).

But Zia must have the right to purchase quality American arms: modern aircraft, helicopters (vital if Soviet troops cross the Pak border), anti-aircraft missiles and radar.

"We are on a tightrope and we cannot stay there forever," Zia said. "When the Soviets start teaching Pakistan a lesson, Pakistan must have at least a fair chance." That argues a powerful case for emergency military supplies -- fast.

Considering that Pakistan now houses, feeds and comforts one of the largest refugee movements in history -- 2 million strong-willed nationalists driven out of Afghanistan by Soviet invaders -- Zia may have a point.