Romanian President Nicolae Ceausescu, in a speech reflecting his country's mounting rift with the Soviet Union, made an emotional plea today for what he called "the sacred right of each nation to decide its own destiny without outside interference."

Ceausescu underscored his opposition to a Soviet demand for higher spending by the seven-nation Warsaw Pact. His speech at a Bucharest rally marking the 60th anniversary of modern Romania was repeatedly interrupted by rhythmic chanting of his name and the slogan "We shall overcome." It was his fifth speech in a week.

Meanwhile, new details have leaked out of the row at last week's summit of Warsaw Pact leaders in Moscow, indicating that the differences between Romania and the rest of the Soviet Bloc are wider than originally believed. According to reports appearing in the usually well-informed Yugoslav press, the Romanians even refused to agree to a statement endorsing the Kremlin's latest assistance to Cuba and the stationing of Soviet Mig 23 fighters on the island.

Clearly infuriated by Ceausescu's disclosures of what really took place at the Moscow summit, the Soviet leadership has called for the strengthening of the Warsaw Pact's defense capability in view of the arms race which it claims is being conducted by NATO countries. So far at least three of its closest allies -- Poland, East Germany, and Bulgaria -- have issued virtually identical statements, implicitly criticizing Romania.

The Soviets went so far as to omit sending the routine anniversary message. A full page of such congratulatory messages was published in the Romanian press today, headed by a cable from China's Chairman Hua Kuo-feng, who visited Romania in August.

Today's speech was viewed by Western diplomats as the climax of a carefully orchestrated campaign by Ceausescu to add another notch to Romania's independence from Moscow.

But Ceausescu hinted at the existence of internal opposition to his hard-line nationalistic regime and he warned Moscow against exploiting these internal difficulties. Differences between socialist countries, he said, "sometimes degenerate into support for counterrevolutionary forces against their own governments.

Despite its long common border with the Soviet Union, Romania has succeeded in transforming itself within two decades from the most obedient of the Kremlin's satellites into the most militantly nationalistic.

Ceausescu's public defiance of Moscow, however, was interpreted by some foreign observers as being motivated by efforts to extricate himself from mounting domestic pressures. These include labor unrest, a generally poor economic situation, discontent among the large Hungarian ethnic minority, and substantial personnel problems within Ceausescu's ruling group caused by the defection to the West of his security chief, Gen. Ion Pacepa.

Today, Ceausescu reaffirmed his insistence that relations between Warsaw Pact countries should be on a basis of equality and national independence. Then he repeated his hints earlier this week that the Soviets had tried to work out an accord on secret new military commitments.

"I did not sign any other pledge or any other document except the declaration which was published," Ceausescu said about last week's Moscow summit. "I reaffirm now with all clarity that we won't sign any documents to engage our countrymen and army, unless it is in conformity with the constitution and the country's laws and with the approval and will of the whole people."

The new crisis within the Soviet bloc is being followed with rapt attention by Yugoslavia, which was the first Communist country to defy Kremlin control in 1948 and has close links with Romania. A lengthy report appearing in the Belgrade newspaper Politika from its Moscow correspondent, Risto Bajalski, today drew attention to many significant omissions in the bland final communique issued after last week's Moscow summit.

Quoting East European diplomats in Moscow, Bajalski reported that Romania had resisted pressure to condemn China, despite a tough speech by Soviet President Leonid Brezhnev at the summit condemning China's new, more active foreign policy.

The Kremlin, which has repeatedly warned the West against playing the "China card," appears particularly worried by any sign of cooperation between NATO and Peking. It is thought this is the main reason behind the Soviet demand for higher military spending by the Warsaw Pact.

According to Yugoslav press reports, Romania is also understood to have rejected a demand that in the event of war the exclusive right to take operative decisions deploying the Soviet Bloc's armed forces would be reserved for the Warsaw Pact's supreme command. This would in effect put Romanian troops under direct Soviet command and explains why Ceausescu is suggesting that no Romanian soldier will ever be allowed to take orders from abroad.

The Yugoslavs believe that Ceausescu also blocked inclusion of a reference praising agreements concluded recently between the Soviet Union and Vietnam in the final Moscow communique. Romania has tried to take an impartial attitude toward the dispute between Vietnam and Cambodia.

It is already known that Romania, the only East European country to recognize Israel, refused to sign a Warsaw Pact statement condemning the current Middle East peace talks in Washington.