President Konstantin Chernenko marks his first year in power Wednesday under a cloud of uncertainties surrounding his health.

Once again the physical infirmities of a Soviet leader have spawned rumors and speculation similar to those that circulated during the last year of ailing Leonid Brezhnev's life and in the final month of Yuri Andropov's brief tenure as Kremlin leader.

Today, an expected meeting between Chernenko and Greek Prime Minister Andreas Papandreou was canceled and again a Soviet leader's apparent inability to assert himself in physical terms is being explained by Soviet officials in ambiguous and convoluted ways -- that he is on "winter holidays" or is not in Moscow or both.

A Greek government spokesman, however, said the meeting had been canceled by the Soviets only a few hours before it was to take place "due to the illness of Mr. Chernenko." He gave no details. Story on Page A24.

Chernenko's illness last summer and the six weeks of hospitalization and convalescence this year have brought back with renewed force the uncertainties at the top that have plagued the Soviet leadership for the past four years.

But the ailments of the 73-year-old Chernenko have created far less apprehension in official circles and the country at large than did the similar problems of his two predecessors.

One reason is that Chernenko has been perceived all along as a transitional leader in a transitional period, who has taken care to follow his predecessor's lead in certain areas of economic change, without appearing to push change too fast.

Another is that the ruling establishment had managed to carry out two transitions without disruptions. Yet another reason is the vastness and inertia of the Soviet bureaucracy that seem to provide stability at a time of crisis.

As a result, Chernenko's health situation seems at this stage to be more of a sideshow to deeper political and social processes going on under the seemingly calm surface of Soviet life, according to senior diplomats here.

Whether Chernenko, when he assumed power, sensed or shared the popular feeling that changes were necessary is not known. Whatever the reasons, during his first year he did not seek to undo what his predecessor, Andropov, had begun.

Thus, the past 12 months were a period of consolidation in which Chernenko continued to keep alive -- albeit without the vigor characteristic of his predecessor -- Andropov's effort to revive the economy and society. Andropov's drive against corruption, inertia and sloppiness continued with somewhat less effectiveness, however.

While there were no new departures in domestic policies, Chernenko did move away from his predecessor's more confrontational posture in foreign affairs. This year the Soviets moved back to the negotiating table with the Americans.

There is an impression here of a leadership seeking to hold the line, lacking both the boldness and imagination to embark on the path of reforms. The power here remains in the hands of old men whose instincts and ideas belong to an earlier period.

One of the clearest indications of this attitude came with the death last December of Marshal Dmitri Ustinov, the defense minister, and the leadership's decision to appoint a 73-year-old career soldier to replace him. Chernenko and other members of the inner circle were simply not prepared to turn over this key job to a younger and more dynamic man.

Ustinov's death was significant for another reason. It removed from public life a unique personality, highly respected for his long political experience and sober judgment. His authority in the ruling council was enhanced by the fact that he had no political ambitions of his own.

His death created a vacuum in the Politburo that was impossible to fill and that is likely to have significant consequences in the long run. Ustinov's voice was instrumental in the election of Andropov to replace Brezhnev and again in shaping the consensus that brought Chernenko to power after Andropov's death last February.

Ustinov's death left Andrei Gromyko, the veteran foreign minister, as the most influential member of the Politburo after Chernenko by virtue of his long experience and high standing in the party.

But Gromyko is 75, Prime Minister Nikolai Tikhonov will be 80 in May and Viktor Grishin is 70. These are the men surrounding Chernenko in the so-called "inner circle" within the Politburo.

It would not be an exaggeration to say that Chernenko's tenure as general secretary of the Soviet Communist Party coincides with one of the most complex periods in Soviet postwar history, involving as it does a search for renewal of the ruling elite.

Old guard Communists who guided the Soviet state throughout much of the four decades since World War II are gradually retiring or dying. The younger men are moving all too slowly into key positions. It is a generational change that is both painful and sensitive and that underlies most of the politicking going on here.

The generational issue is complicated by economic difficulties and differing views on how to deal with them -- whether to seek ways for major reforms or to build on and improve the existing system.

The Russians in general are a conservative people. Even those who desire changes fear them at the same time. The centralized nature of the system only enhances conservatism and inertia.

While his tenure was a brief one, Andropov's 15 months in office were a period of extraordinary dynamism and change. After the stagnation and apathy of Brezhnev's waning years, the Soviet Union appeared to be setting a new course.

In particular, Andropov sought to invigorate the party bureaucracy by pushing forward younger men. During Brezhnev's 18 years in power, Soviet officials came to regard their positions as carrying life tenure. At the last party congress in 1981 the entire membership of the Central Committee, the party's decision-making body of more than 300, was reelected. By contrast, Andropov during his short leadership changed more than half of the 18 Central Committee department chiefs -- the men who wield greatest authority in their fields of responsibility.

It is possible to imagine the reaction of numerous officials both at the highest levels and throughout the bloated apparat that runs the country. The resistance to change was all too obvious.

The selection of Chernenko to replace Andropov a year ago was in itself a demonstration of the ruling establishment's innate conservatism. Chernenko was not only the closest aide of Brezhnev but was viewed here as his political heir-apparent.

In the succession struggle during 1982, Chernenko relied on his mentor's power base and espoused his policies. In a significant way, Chernenko seemed fully identified with his generation, whose view of the world was shaped in the 1930s and 1940s.

Andropov, on the other hand, identified himself with tendencies for change and reforms. While only three years younger than Chernenko, Andropov seemed to reflect the views and aspirations of younger and better-educated generations.

Andropov's victory over Chernenko in November 1982 did not mean a resolution of generational conflicts within the ruling establishment. His success resulted from institutional alignments with the armed forces and from the KGB backing the man who had served as its chief during the preceeding 15 years.

In the current situation, it is inevitable that attention of western diplomats and journalists be turned to succession.

Oddly, if the recent pattern of succession holds true, the youngest member of the Politburo, Mikhail Gorbachev, could be expected to become the next Kremlin leader.

Although only 53, Gorbachev has amassed all the key positions and responsibilities to qualify for the job. He now holds the unofficial position of the number two official in the party, the same spot where Andropov was when he succeeded Brezhnev and where Chernenko was when he succeeded Andropov. Moreover he is one of only two men -- the other is Grigori Romanov -- who sits on both the Politburo and party secretariat. In the past, the combination of the two positions was necessary for anyone aspiring to the top position.

Gorbachev is the party's second secretary in charge of ideology and chairman of the Foreign Affairs Committee of the Supreme Soviet, the national assembly. He was pushed forward by Andropov and seems to enjoy the support of his mentor's constituency.

Another Politburo member who could be considered a candidate for the top job is Romanov, 61. He is a Central Committee secretary in charge of the military-industrial complex.

Whether the leadership is prepared to turn the reins of power to a younger man is unclear. There has been speculation in normally well-informed Soviet circles that yet another member of the old guard may be picked for the job. For the first time the name of Gromyko has been mentioned, although he is considered a long shot at best.

The situation is expected to become clearer on Feb. 22 when Chernenko is requred to make a speech to his constituency in the current election campaign for the Supreme Soviet of the Russian Federation.

Chernenko has not been seen in public since Dec. 27. An official communique, however, said that he attended the meeting of the Politburo last week and talked on agricultural issues.

The prevailing view here is that if Chernenko is physically unable to deliver his Feb. 22 speech to the Supreme Soviet, it can be assumed a new transition is under way.