Remnants of a leftist guerrilla force believed to have been wiped out in the late 1960s have re-emerged in four parts of Guatemala, according to U.S. intelligence sources and sources within the Guatemalan army.

The newly active guerrillas' most successful action so far was the daylight kidnaping of El Salvadors' ambassador in May during a meeting here of the governors of the Inter-American Development Bank. Ambassador Eduardo Casanova was released had been read at the bank meeting after a six-page guerrilla communique and published in local newspapers.

The guerrillas, believed to number about 300, now call tehmselves the Guerrilla Army of the Poor. U.S. and Guatemalan sources believe that the group descends directly from the Revolutionary Armed Forces, a group started by U.S. trained Guatemalan army officers in the early 1960s that once controlled large parts of the country.

U.S. sources say the new group's leader is Cesar Montes, who joined the older group in 1962, when he was a 20-year-old law student. Montes was a leader of the orignial guerrilla group until it was crushed by the army with U.S. support in the late 1960s.

The Guatemalan army has charged that Cubans support and lead the guerrillas in the field. Later it revised its statements to say that the Cuban advisers were based in neighboring Belize. These charges have not been confirmed by other sources.

Since the Central Intelligence Agency helped overthrow a leftist government here in 1954, the powerful Guatemalan army has often cited the threat of communism to obtain U.S. support.

The Guerrilla Army of the poor reportedly has four independent commands, three in the countryside and one in the capital. They have been most active in propaganda and organizing in El Quich, a cool mountaineous region to the north of Guatemala City, inhabited almost exclusively by Indians who still speak Mayan dialects.

Near Escquintla, along the tropical pacific coast, the guerrillas have been harassing large landowners. There have been many reports in the last six months of armed men, "dressed in olive green" (the press catch phrase) burning fields of sugar cane.

The third rural cell, in the semi-arid Zacapa department, has been less active, but it was there that the guerrillas had their strongest support 10 years ago.

The guerrillas do their recruiting both in the courtryside and at the universities, islands of antigovernment activity.

The guerrilla unit in the capital is a special case. The influence of the over banned Communist Party - known as the Guatemalan Labor Party - is greatest here. U.S. and Guatemalan officials agree that the guerrillas are not under Communist command, but add that they often work in uneasy alliance with the party. A large percentage of urban guerrillas are Communist Party members, the sources say.

Tensions between the two groups go back 15 years. Cesar Montes was once a member of the Labor Party's Central Committee, but he reportedly resigned from the party in 1968 to protest its failure to support the guerrillas fully. Guatemalan President Gen. Kjell Laugerad told a group of foreign journalists in May that a Labor party delegation had traveled to Cuba to ask Fidel Castro to stop supporting the guerrillas, because of the intense pressure the army was putting on the party as a result of guerrilla activity.

U.S. sources here do not agree with the Guatemalan army's belief that the guerrillas would collapse quickly if Cuba withdrew support. An American embassy official said that Cuba is backing the rebels in only a limited way. There are no Cubans with the guerrillas, nor is Castro donating huge sums of money or arms, he said.

"The guerrillas would continue if Castro disappeared. They are not dependent upon foreign support," this official said. He listed their kidnapings and arms robberies as evidence of their self-reliance. Some are believed to have had training in Cuba or visited the island for rest and recuperation.

U.S. and Guatemalan authorities also disagree about the source of imported arms.

"They come down from Mexico," said another American official. This is the same route the guerrillas used in the 1960s. The Guatemalan army is convinced, however, that Cuba sends the arms directly by sea into Belize, a British colony that Guatemala claims.

The U.S. embassy does not take the guerrillas lightly. One week before the Casanova kidnaping, an embassy official stated that the Guerrilla Army had been laying the groundwork carefully for two years, and was primed for something spectacular.

"The guerrilla problem is going to get worse," he stressed. In the short run, though, neither Guatemala nor the United States expects the guerrillas to threaten the government.

In March of this year, Guatemala rejected further U.S. military aid because of unfavorable U.S. reports on violations of human rights here. The aid had been averaging $2.1 million a year, only a small part of the military budget.

The long-run potential for instability exists. Guatemala's population remains overwhelmingly rural, Indian, and poor, cut off ethnically and economically from participation in national life. Guatemalans and Americans who work in the countryside, say peasants are much more aware of their condition now than they were just ten years ago. The transistor radio has brought the outside world to the most remote village. The burgeoning rural cooperative movement has fostered a sense of working together among the traditionally individualistic Indians.

The most immediate challenge to order will be the presidential elections, scheduled for March of next year. Campaigns are tense periods, when death squads of both the right and the left strike. The three main candidates are high-ranking army officers, two generals and a colonel.