China is now on the United States' side in the worldwide struggle against the Soviet Union -- largely on the basis of the old proverb that "the enemy of my enemy is a friend." Faced with this reality, the National Security Council has been curious about what the Chinese have been up to in Africa that may affect American interests there.

The best answer so far has been in a secret report by the Central Intelligence Agency a few weeks ago. The document, reviewed by my associate Dale Van Atta, represents the current information on which the Reagan administration is basing its policy in Africa.

"Over the past quarter of a century," the CIA reports notes, "[Peking] has attempted to project its influence in Africa with varying degrees of intensity and for a variety of purposes.

"Relative to Chinese interests parts of the world, [Peking's] interest in Africa is small, and both African and Chinese leaders are aware that China's influence in the continent is marginal." The report adds, however, that there is no reason to suggest that Chinese interest in Africa will not increase.

"Today, the principal objective of Chinese policy in Africa is to check the spread of Soviet influence," the CIA report continues. "The major focus of [Peking's] effort has been in southern Africa, where Moscow has been especially active for the past five years."

The intelligence analysts point out that China has followed random policies in Africa over the past few decades, but that in the last three years a revitalized, better coordinated policy appears to have emerged. As the CIA experts see the situation, Chinese policy has not focused "on its prime objective and [takes] into account the limited resources it has to spend on an arena far from its own borders."

The key elements in the current Chinese policy toward Africa, as the CIA understands them, are:

"Exhort southern African states to be wary of Moscow."

"Advise the West -- especially the United States -- to provide military and economic assistance to states in the region, and to press South Africa to abandon its claim to Nambia and its domestic policy of apartheid."

"Urge liberation movements in the region to unite to oppose both colonialism and Soviet hegemony."

"Aid liberation movements with small arms and training if they show promise of being effective and not committed to Moscow."

How Peking expects to accomplish this ambitious program without a far greater commitment of money and effort, the CIA report does not say.

As for the future course of Chinese activity in the continent, this is what the CIA analysts have predicted:

"[In] the coming decade, China is likely to seek to enhance the stability of states that it believes are not under Moscow's thumb and have a chance to remain in power." This encouragement presumably would include economic assistance, if not outright military support.

"With regard to regimes friendly to Moscow, or perceived to be inherently unstable, China is likely to press for evolutionary change or, if compelled by competition with Moscow, revolutionary change sponsored by anti-Soviet resistance movements," the CIA report predicts.

In short, intelligence experts see the possibility that China would invest significant amounts of economic and military aid to encourage "destabilization" of Soviet-dominated regimes -- though Peking would prefer not to be forced into such a situation.

As for the specific regimes that might become embroiled in the power struggle, the CIA reports that, so far at least, Tanzania and Zambia, which have longstanding ties to China, "remain friendly," though both countries maintain relations with the Soviet Union.

At the other end of the scale, according to the CIA, is Mozambique, which maintains formal relations with Peking but, like Angola, remains "close to Moscow."

"China's greatest success has been with Zimbabwe," the CIA report states. There, "the ruling party, once a Chinese client, remains loyal to [Peking], cool to Moscow and committed to economic and political involvement with the West."