President Carter decided to link the strategic interests of the United States and Communist China at a luncheon May 16, when his national security advisers reversed a ban on sales of airborne scanning equipment to Peking.

This decision was agreed to by Secretary of State Cyrus Vance, Secretary of Defense Harold Brown and National Security Adviser Zbigniew Brzezinski. The move was withheld from the bureaucracy because Brzezinski wanted to break the news himself when he arrived in Peking four days later.

The decision permitting the sale of the formerly circumscribed technology opened the door for a policy move of global proportions, referred to in Washington as "playing the China card." Besides its effect on U.S.-Soviet relations, there are domestic implications: A common U.S.-Chinese stance against Moscow is intended to convince conservatives in Congress that formal diplomatic ties with Taiwan should be abandoned in favor of Peking.

The scope of the Peking talks, much broader than was publicized, included the following:

Item: Brzezinski specifically raised with Chinese leaders, including Chairman Hua Kuo-feng, his hope that China would use its influence with black Rhodesian guerrilla leader Robert Mugabe to support the Anglo-American settlement. Mugabe, who has intimate political connections with Communist China, is by no means committed to free elections as desired by London and Washington.

Item: Brzezinski raised the hope that Peking would encourage Mozambique's Marxist leader, Samora Machel, to deny Rhodesian guerrillas their bases along the Rhodesian-Mozambique border.

Item: For the first time since the warming trend started in Sino-American relations, the president authorized Brzezinski to conduct counterpart talks with Chinese experts in two fields: science-technology and military. The U.S. military expert accompanying Brzezinski was Morton Abramowitz, deputy assistant secretary of defense for international security and subsequently named the new U.S. ambassador to Thailand.

That choice for the U.S. embassy in Bangkok was itself symbolic. Abramowitz, a Far Eastern expert, is regarded in Peking as uniquely suited for a post in a nearby Southeast Asian country not susceptible to Soviet pressure.

China's nightmare is "encirclement" by vastly superior Soviet power - a principal topic in Brzezsinki's world strategy talks with China's new leadership. The U.S. team was particularly impressed with Chinese recitation of Soviet machinations in unified Vietnam. Emigration from Vietnam of hundreds of thousands of ethnic Chinese has resulted from political and cultural persecution, which Peking believes has Moscow's strong backing.

Brzezinski found Chinese perceptions of Soviet world objectives close to his own and those now developing elsewhere within the administration. While obsessed over alleged Soviet encirclement of China, Hua and his men showed great distress also over Soviet penetration of Africa and Afghanistan.

They perceive Cuba's Soviet-backed role in Angola as another ploy for Soviet control of a belt of southern African states from the Atlantic to the Indian Ocean. Zaire is the gap in that belt; if closed, the Soviet belt would cut off Rhodesia and South Africa from the rest of Africa.

Accordingly, Chinese leaders listened sympathetically when Brzezinski suggested that Peking do in Angola what the U.S. Congress forbids the United States from doing: strengthen Lucas Savimbi's Angolan guerrillas now fighting a civil war against Agostinho Neto's Soviet-backed regime.

The sweep of these U.S.-Chinese talks was breathtaking, once the decision to clear that airborne-scanning technology for China symbolically opened them. They were also helped when Brzezinski let it be known in Peking the United States would now encourage its European allies to sell defensive - but not offensive - weapons to China.

Left unresolved by the Peking talks was the Taiwan question. Some U.S. officials are certain that early next year Carter will begin disengaging from Taiwan - thereby triggering a battle not to be confined to Capitol Hill.

To prepare for that, administration strategists are quietly briefing key congressmen - including staunchly conservative Republicans - about the administration's new link with Communist China on global strategy. The hope: affinity with Peking in containing Soviet power will override passionate conservative support for Taiwan.

Skepticism about playing the China card is intense among the conservatives wooed by Brzezinski and his men. But their tacit cooperation may be essential to carry forth into practice the bold talk between Brzezinski and Hua in Peking.