The condition of President Tito's left leg worsened further today but, according to Yugoslav sources, the 87-year-old marshal was strongly resisting medical advice that it should be amputated.

While an official medical communique only said that Tito's condition is "slightly worse" but that he had spent a "peaceful night," the picture presented privately by presumably well-briefed Yugolsav journalists is of a proud and stubborn man who wants to be remembered as a symbol of activity and vitality -- not as a chronic invalid. b

Tito's reported opposition to amputation leaves his eight-man medical team with the agonizing choice of overriding his wishes or allowing possible gangrene to set in and spread to other parts of the body. Surgeons have already failed in their attempt to bypass a blood clot in his leg with an artificial duct during an operation last weekend.

Despite an optimistic gloss to the terse daily statements issued by the medical council, most Yugoslavs believe that their ruler for the past 35 years is fighting for his life.

Tito was also reported to have rejected a proposal to U.S. heart specialist Michael De Bakey last week that he go to Houston for special care. De Bakey could not be reached for comment.

Arrangements for a smooth transition of power are reported to be well in hand and Yugoslavia has been placed on a general state of alert against any attempts to exploit the situation by either pro-Soviet groups at home or extreme nationalist exiles abroad.

Yugoslav officials, meanwhile, professed to be embarrassed by Western speculation over the possibility of Soviet moves against Yugoslavia after Tito's death. Earlier the official Soviet news agency Tass attacked as "crude, provocative, and false" what it described as "the fantastic concoctions in the Western press trying to ascribe anti-Yugoslav intentions to the Soviet Union."

One Yugoslav Communist Party official commented: "These reports only do us a disservice. They irritate the Russians at a time when they are irritated enough already. The Soviets are watching Western reaction very closely -- and this is allowing them to pose as defenders of Yugoslavia."

The reaction reflects the complex nature of Yugoslavia's relationship with Moscow and its ambivalent attitude towards the West. The Yugoslav Communists, who succeeded in breaking away from the Soviet bloc in 1948, welcome international attention and support -- but with the proviso that they are not associated with any overtly anti-Soviet campaign.

So far reports on Tito's illness in the officially inspired Yugoslav press have been restricted to brief statements from the clinic in the regional Slovene capital of Ljubljana where he is being treated. Workers and Communist Party members, however, are being kept informed of developments at factory and office meetings.

Inevitably, rumors abound. According to one unconfirmed report, students at the University of Zagreb demonstrated earlier this week in protest against the Soviet intervention in Afghanistan. They are alleged to have shouted: "Danas Afghanistan, SUTRA NAS STAN " -- a play on words in Serbo-Croat meaning "today Afghanistan, tomorrow our own home."

One complicating factor is that Tito is also reported to be suffering from arteriosclerosis and diabetes. After the failure of last weekend's operation, it is believed that surgeons would want to wait at least a week before operating again.

Most foreign observers believe that in the event of Tito's death, the immediate transition should proceed fairly smoothly. His functions as head of state and president of the Yugoslav League of Communists will be taken over by collective bodies chaired in annual rotation by representatives of each of Yugoslavia's eight republics and autonomous regions.

But how long this elaborate mechanism will work is open to question. There is already some talk that the concept of collective leadership will have to be supplemented by the guiding hand of one or more of the party veterans. An obvious candidate for this kind of role would be the Croat leader Vladimir Bakaric, 67, who already has overall responsibility for the country's security and is one of the few survivors of the wartime inner circle around Tito.

An alternative solution would be for Yugoslavia's different national groups to agree on a compromise figure acceptable to all the different factions. This might lead to the emergency of a relatively unknown politician as the country's future leader.