NEWS ANALYSIS : Timing of Yeltsin Nose Job Baffles Russia : Leadership: Aides see nothing ‘sensational’ in his undergoing surgery after ordering drive on Chechnya. Critics accuse president of hiding.

What a time for a nose job.

Why would the president of a major power decide to enter the hospital for optional surgery to repair a deviated septum in his nose--surgery that aides said would require a recovery period of up to eight days--immediately after approving a controversial invasion of a rebellious province?

Yet that is exactly what Russian President Boris N. Yeltsin has done, prompting his fellow citizens once again to ponder the erratic performance of their leader, the state of his health and the degree of control he wields over his powerful Kremlin aides.

On Friday, the fiery 63-year-old Siberian, whose popularity is at an all-time low, authorized the Russian government to “use all means at the state’s disposal” to subdue the breakaway Muslim republic of Chechnya.

Then he entered the hospital for what aides described as a two-hour procedure on his nose. At dawn Sunday, Russian troops and tanks began rolling toward the Chechen capital of Grozny, a military intervention that many fear could spill much Russian blood.

Vladimir Ilyushin, one of Yeltsin’s closest aides, said the president, who has a history of back problems, heart trouble and unexplained absences during crises, had recently had trouble breathing through his nose, particularly at night.

“I don’t see anything sensational about this, although these are complicated times,” Ilyushin said. “You only have one health.”

On Monday, Kremlin aides said Yeltsin was in complete control and would be back in his office in a few days. They said the president would soon be able to receive foreign diplomats but would not be able to speak to journalists for a time because his speech is not clear enough.

On Tuesday, as reports reached Moscow that nine Russian soldiers had been killed fighting in Chechnya, Yeltsin gave a brief interview from his hospital bed. “No big war will start. The conflict so far is not even spreading out of Chechnya,” he assured the newspaper Argumenti i Fakti.

“The doctors say the operation was successful,” Yeltsin added. “I feel not bad.”

“Boris Yeltsin is a coward,” said entrepreneur Konstantin N. Borovoi, head of the Economic Freedom Party, at an anti-war demonstration in Moscow. “The fact that he decided to undergo a nose operation shows that he really no longer controls the situation in the country. He has let matters get out of hand and decided to ‘take a break’ in a quiet clinic.”

Some Russians suggested a different explanation for the sudden hospitalization of a head of state who recently stood up the prime minister of Ireland and then blamed his bodyguards for not allowing aides to wake him up in time.

“Maybe he took too much of his favorite medicine,” suggested Caucasus scholar Sergei A. Arutiunov, referring to Yeltsin’s rumored vodka habit.

Others viewed his reported illness with deeper concern.

“I’m very worried about what happened to him,” said Alexei G. Arbatov, who heads a Moscow think tank. “I have very many suspicions that it’s not the nose.”

Yeltsin has been hospitalized for heart trouble twice, in 1987 and in 1990. He dropped out of sight for short periods during the political upheavals of 1991 and 1993, and has admitted to bouts of depression.

Whatever the truth about the presidential proboscis, Yeltsin is once again in a deep political crisis.

Three and a half years into his six-year term, Yeltsin’s popularity rating has dropped to a new low.

A poll of Muscovites by the firm Mnenie last month found that only 40% want him to continue as president and 33% would like him to resign. In May, the same poll found 53% supported Yeltsin and 24% wanted him to quit.

His political foes--who now include democrats as well as nationalists and Communists--are calling for presidential and parliamentary elections next year. If Yeltsin is forced to acquiesce, the outlook is not promising.

In a by-election in the city of Bryansk last weekend, Communists and nationalists won seven local legislative seats, and independent candidates took the other two. The democrats failed to field a candidate. If Yeltsin was following the election news from his hospital bed, the only consolation was that the candidate actively supported by ultranationalist Vladimir V. Zhirinovsky was beaten soundly.

Worse, some of the stalwart liberals who were Yeltsin’s last allies have turned against him.

Sergei N. Yushenkov, chairman of the Parliament’s Defense Committee, on Monday said Yeltsin’s policy on Chechnya was aimed at justifying a crackdown in Russia and at “introducing dictatorship.” He said Yeltsin no longer consults with his former democratic allies and has no respect for their advice, while his entourage has lost all ties with reality.

Then, on a holiday celebrating the Russian constitution, the prominent democrat called on his colleagues to use the year-old document to impeach Yeltsin.

Economist Yegor T. Gaidar, head of the Democratic Choice of Russia party, quickly disavowed Yushenkov’s remarks. But Gaidar has broken with Yeltsin over Chechnya, as have human rights leader Sergei A. Kovalyev and other leading lights of Russia’s democratic transformation.

Gaidar, a former acting prime minister and the first architect of Yeltsin’s free-market economic reform, told the “Itogi” television program, “I tried to reach Boris Nikolayevich but I did not succeed, for the first time in many years.”

Yushenkov’s telephone was cut off altogether--a tactic Yeltsin has used against friends-turned-critics.

Two years ago, Yeltsin sacrificed Gaidar to appease the right-wing critics who opposed “shock therapy” reforms as too painful and who then turned to a more potent brand of nationalism. Reforms have continued, though with more fits and flaws than many had hoped. Inflation running at 14% per month in November has yet to be tamed.

Critics sought to portray the Russian president as an isolated captive of his power-hungry men.

Borovoi charged that Kremlin “riffraff” are running the crackdown on Chechnya under the direction of Gen. Alexander V. Korzhakov, the head of Yeltsin’s bodyguard service, who is now considered one of the most powerful men in the Kremlin. Yeltsin once described himself and Korzhakov as “inseparable.”

But Foreign Minister Andrei V. Kozyrev, who supports the Chechnya intervention, warned that if democratic forces are linked in the public mind to “disintegration, anarchy and muddle,” Zhirinovsky and the Communists will be seen as the alternative.

Critics say Yeltsin has already adopted many of Zhirinovsky’s policies. Democrats charge that Yeltsin has developed a case of the same political disease that proved fatal to former Soviet leader Mikhail S. Gorbachev: compromising real reform to appease political conservatives, and in the process alienating the liberals and reformers who were his only true allies.