United Nations, N.Y. — For months after the Falklands war, South America seemed to have put its many territorial disputes on the back burner.
But now Venezuela and Guyana - neighbors on the northern bulge of the continent who have had many disagreements - are turning up the heat on their dispute over the Guyana Essequibo, 53,000 square miles of rain forest held by Guyana since 1899.
This month Venezuela, by far the richer and militarily more powerful of the two nations, indicated at a conference of nonaligned nations that it would not reject use of force to gain control of the disputed region.
Some of its tough talk may stem from its desire to get its hands on the diamonds, uranium, and gold it believes may lie in the Essequibo. There are reports the region also may be rich with offshore oil.
The government's ominous statement may also be campaign talk related to Venezuela's presidential election, which is scheduled for next year. The ruling COPEI-Social Christian Party is considered in political trouble.
A formal 12-year moratorium on Venezuelan efforts to gain hold of the area ended last June - and now Venezuela has refused to renew it.
For Guyana, which gained independence from Britain in 1966, loss of the Essequibo would be an almost unbearable blow. The territory constitutes five-eighths of the nation's land and is undoubtedly the richest section of Guyana, if only for the potential water power if the region's Mazaruni River is dammed.
United Nations Secretary-General Javier Perez de Cuellar is trying to induce the governments to reason together, an exercise he calls ''preventive diplomacy.'' At this point he is not mediating between the two but simply trying to get them to agree on a mechanism for resolving their quarrel peacefully.
As far as such talks go, Venezuela says it prefers negotiation as a means of settlement; Guyana leans toward the judicial process.
But there have been recent reports of Venezuelan military concentrations on its side of the border and of repeated aerial violations of Guyana's territory. Venezuela's military strength is far greater than Guyana's. It has some 2.5 million men trained for military service; Guyana has only 154,000.
A right-wing Venezuelan Army faction reportedly wants a military strike against Guyana. ''Its fingers are itching,'' a Latin American ambassador says. This may be one reason the Venezuelan government is sounding off. ''The (political) parties cannot back off at this stage without running the risk of appearing to lack patriotic ardor,'' according to the diplomat.
Leaders of the nonaligned movement and the British Commonwealth have clearly indicated to Caracas their formal opposition to any aggression against Guyana. But a well-placed Latin American diplomat told The Christian Science Monitor: ''If I were in the President of Guyana's shoes, I would worry.''
Latin American observers are convinced that Venezuela vigorously supported Argentina against Britain in the Falklands war because it anticipated a possible similar confrontation with Guyana.
Twelve years ago, observers say, Venezuela contemplated a military move against Guyana but held back on the advice of Brazil. And Brazil reportedly has advised Venezuela not to move agaisnt Guyana now, either.
However, Brazil was reported last month to have sold several reconnaissance planes and armored personnel carriers to Guyana. Wire services quoted Guyanese President Forbes Burnham as saying he had to ''make preparations'' for the ''possibility of armed conflict'' with Venezuela.
The existing borders between Guyana and Venezuela were drawn by an arbitration tribunal in 1899 and accepted by Venezuela as a ''full, final, and perfect settlement.''
But in the 20th century Venezuela came to see that decision as void. In 1966 the two countries signed an agreement to try to resolve the dispute. But talks failed and in 1970 Venezuela agreed to a 12-year moratorium on its claim.