After providing Ronald Reagan with some of the best preelection publicity he could hope for, China will play host to the most senior Kremlin official since the two Communist giants parted ways in the early '60s.
The American President arrives in China today to exchange congratulations with Chairman Deng Xiaoping and other Chinese leaders on improved ties between their countries. They will also discuss arms sales, a nuclear agreement, and, no doubt, the ''Soviet threat.''
China's Soviet guest, First Deputy Prime Minister Ivan V. Arkhipov, will visit in mid-May. He is coming, it is believed, largely to discuss trade - but more important, to act as a counterbalance to Mr. Reagan's visit and the high profile that it will give the healthy state of Chinese-American ties.
But as relations between China and the United States improve, it is becoming tougher for China to maintain its precarious balance between the US and the USSR.
On several occasions in the past year, including during the visit of US Defense Secretary Caspar Weinberger in September, China has publicly stated that the Soviet Union poses the greatest threat to China's security.
And although Peking still regularly attacks both the US and the Soviet Union for their hegemony and nuclear-arms buildup, it is to the US that China is now turning for arms and assistance in developing its fledgling nuclear power industry.
During his visit, Mr. Weinberger reportedly presented the Chinese with a list of military items that the US is willing to sell China, including antiaircraft weapons and antitank guns.
Besides wanting to buy American high technology, Peking also would like to see US firms participate in building nuclear power reactors for China. It is keen to see a nuclear cooperation pact signed during the President's visit, which, US officials say, is all but certain.
China wants to be seen as conducting a foreign policy independent of the US and USSR. The bargaining power such a position provides has encouraged China to try to match in its relationship with the USSR the improvements in Sino-US ties.
For this reason, China and its official press point to the four rounds of Sino-Soviet normalization talks as evidence of ''progress'' in their relations.
In reality, the Chinese-Soviet consultations, which began in early 1983, have yielded nothing to match the growth in Sino-US relations. Despite the resumption of some cultural and sporting exchanges and a boost in trade, neither China nor the USSR has altered its stand on the three substantive issues that bar normalization.
These ''three obstacles'' involve the Soviet presence on three sides of China - in Afghanistan, Mongolia, and Vietnam. China also includes the Soviet-backed Vietnamese invasion of Kampuchea (Cambodia) as one of the ''obstacles.'' China has made clear that there can be no normalization without Soviet concessions in these areas.
A spokesman for the Chinese Foreign Ministry said last week that although there had been progress in the talks, this central problem had not been solved.
After last month's talks, both sides pledged further efforts toward normalization. However, the Chinese spokesman said, ''On the question of how relations can be normalized, significant differences still remain between the two sides.''
For its part, the Soviet Union is committed to the enormous investment in military resources it has made in the past decade as part of its policy toward China. It has ruled out discussion of China's ''three obstacles'' on the grounds that these affect its relations with countries other than China. Initial indications are that President Konstantin Chernenko is likely to preside over an even harder line toward China than was seen under the more conciliatory policy pursued by Yuri Andropov.
Despite this stalemate, the bargaining power that continued contact with the Soviets gives China in its dealings with the US has enabled Peking to pressure Washington on issues such as arms sales to Taiwan and technology transfer to China. This is despite straightfaced denials by Peking that it is conscious of balancing the two relationships.
''There exists no such matter of moving closer to one power or another,'' a Chinese Foreign Ministry spokesman said last week. ''A bias is not there. China pursues an independent and peaceful foreign policy. . . . We play neither the Soviet card nor the US card.''
Perhaps when a Soviet president is also welcomed in Peking, the cards will really have been put away.