Soviet President Leonid Brezhnev would probably be unable to conduct serious negotiations personally with President Carter at a summit meeting and may be nearing the end of his rule because of age and ill health, senior French officials have concluded.

These impressions, formed during the Soviets leader's three-day visit to France last week, were evidently relayed by Predident Valery Giscard d'Estaing to Secretary of State Cyrus Vance at a meeting here last Friday, according to officials in Paris and Washington.

"There were no real exchanges of views during the three days and certainly no negotiating," said one well-informed source. "The agreements that were signed by the two men had been agreed upon before. Breahnev was not in any condition to negotiate here, and it is certain that Giscard told Vance that he was not likely to be in any condition to negotiate seriously and personally with Carter."

French officials speculate from this that any American-Soviet summit would have to be scrupulously prepared beforehand at lower levels with a Carter-Brehnev meeting being merely a ceremonial finale.

President Carter said yesterday that he "would welcome a chance this year to meet with President Brezhnev." His press conference statement may reflect the new sense of urgency developing here about dealing with the Soviet leader, who is 70.

The offer drew a terse, negatively worded Soviet announcement that "preliminary" discussions were being held on such visit. Officials here noted, however, that the Carter administration has now established publicly that a failure to schedule a summit is not Washington's responsibility.

The somber impressions relayed to Vance of Brezhnev's state of health appear to spring largely from a 15-minute private session Giscard had with Brezhnev June 22, the only time the two met without aides during Brezhnev's visit, his first trip to the West in two years.

Surrounded by aides, Brezhnev dominated the first two days of the discussions. He read, at times forcefully, from prepared statements that offered no openings for exchanges of views, according to French sources.

It was from these group meetings that the initial impressions of Brezhnev staying in full control despite showing his age were formed, and relayed to the press by the French delegation.

Officials present at or briefed on these two sessions continue to describe Brezhnev's preformance as an active one in view of his age and appearance in recent years of having serious health problems.

But Giscard appears to have come away from the private meeting with a far grimmer view of Brezhnev's health. Initially scheduled as an hour-long, head-to-head meeting, the June 22 private talk was pushed back an hour at Brezhnev's request then scaled down to 30 minutes.

In fact, the talk lasted only 15 minutes, and Giscard reportedly depicted Brezhnev to Vance as having failed to engage in any meaningful discussion in the meeting. According to one version that could not be confirmed. Vance was told that the Soviet leaders's conversation wandered when his aides were not around.

"Brezhnev's handlers handled him far more than they ever before," said one diplomatic source. "He tired more rapidly than ever before."

The Soviet insistence on having Foreign Minister Andrei Gromyko, Foreign Trade Minister N.S. Patolichev and lesser officials sit in on the talk throughout the first two days continues to intrigue French officials.

The French delegation arrived at the 14th Century chateau in Rambouillet, southwest of Paris, expected Giscard and Brezhnev to go immediately into brief private talks. Instead, they found that the Soviets had set up two separate tables with 10 chairs each in the meeting room.

The trip from Moscow appears to have contributed significantly to the very fatigued appearance Brezhnev had in the second and third day of talks, and what appears to have been some disorientation in the brief private session with Giscard.

In Moscow, two weeks earlier, during his meeting with French Foreign Minister Louis de Guiringuad, Brezhnev started slowly, but gradually warmed up in their hour-long talk and spoke forcefully without notes, according to one report.

At Rambouillet, "we certainly did not see a man at death's door," said one official, who denied that the French had seen any signs of a serious illness in Brezhnev.

But, the official added, Brezhnev never completerly recovered from the air journey. He appears to have begun a steady decline because of old age and his medical history that may force him to step down before the end of the year, according to this view.

It could not be established from French sources that Giscard had conveyed to Vance a similar estimate on the apparent opening of a transition period for Soviet leadership. There have been indications, however, that Vance carried that message home.

Brezhnev reportedly ate little more than soup at the state dinner Giscard gave for him, and appeared to be displeased with the cooking at the Soviet embassy here during his reciprocal lunch for Giscard.

Despite the indications of the concern expressed by Giscard to Vance, both French and foreign sources were cautious in making predictions about Brezhnev's health in the immediate future. One source pointed to Gromyko's virtual disappearance for two months earlier this year, evidently because of fatigue, and the strong comeback the foreign minister has made since March.