The Reagan administration has agreed to sell 24 F16 fighter planes to Venezuela in what would be the first delivery of such advanced U.S. weapons to a Latin American country in almost a decade and a significant step in Venezuelan efforts to fill what it regards as a vacuum of influence in Latin America.

The warplanes deal, under which Venezuela would pay some $500 million for 18 F16s and 6 F16Bs, a training model of the plane, is expected to be forwarded to Congress by the administration later this month, although there is a slight chance the action could be postponed or modified as a result of controversy over sales of AWACS electronic-surveillance planes to Saudi Arabia and F16s to Pakistan, officials here and in Washington said. If approved, delivery of the Venezuelan planes would begin early in 1984.

The agreement would represent the first sale of such sophisticated warplanes to Latin America by the United States since the Nixon administration announced in 1972 that such deals could hurt economic development and increase instability in the region. U.S. officials acknowledge that the breaking of the ban is likely to increase pressure from other Latin American governments for U.S. military equipment.

Nevertheless, administration officials feel the sale is justified by Venezuela's growing importance as a supporter of U.S. policy in El Salvador and elsewhere in Latin America, and by what is perceived as the increased threat from Cuba, whose relations with Venezuela have recently deteriorated.

Venezuelan officials say the F16 purchase, part of a program of upgrading the armed forces, complements what they see as a growing Venezuelan effort to establish an influence in the region independent of the superpowers.

Despite Venezuela's identification with many U.S. actions in the region -- a closeness that is regarded with suspicion by some other Latin American countries -- the government here has pursued its own forceful program of political intiatives and development aid and has differed with the Reagan administration on several points, including support for Nicaragua and relations with the dictatorial regimes of Central America and South America's southern cone.

As a result, the Venezuelans believe they are "filling a gap left by the United States" in Central America and the Caribbean, said Haydee Castillo de Lopez, a leading member of the governing Christian Democratic party. She said the party maintained an "energetic refusal to be the middleman for the United States" in the region, adding, "The United States has neglected its interests through misperceptions of social and political reality."

In Nicaragua, for example, Venezuela has continued substantial economic aid to the Sandinista government even while criticizing its arms buildup and leftward course, and officials here maintain that the Reagan administration -- with its cutoff of aid -- has lost the ability Venezuela has to influence the course of the Sandinistas.

"We want Nicaragua to have a pluralistic democracy," Castillo de Lopez said. "And it is not by abandoning Nicaragua that we can do that."

Nicaragua is included in a $1 billion annual program of Venezuela and fellow oil-producer Mexico to supply and subsidize petroleum for 11 Central American and Caribbean countries, and Venezuelan officials frequently cite the program as an example of their independent strategy.

President Luis Herrera Campins emphasized this careful separation of Venezuela's interests from the United States in a press conference for American reporters this week, saying "it is not in reality clear what the policy of the United States is to those countries" of Central America.

Herrera said the Reagan administration in its first months "abused the threat" of armed intervention in El Salvador and elsewhere at the expense of its own prestige. Referring to relaxation of U.S. pressure on military dictatorships in the area, Herrera warned that the United States could not "continue following a policy of sustaining dictatorships as it has in the past." During the Kennedy and Carter administrations, he added, Latin American dictators "at least had the impression that they were not explicitly backed" by Washington.

Venezuelan officials like to point out that Herrera's government was supporting fellow Christian Democrat President Jose Napolean Duarte of El Salvador long before the United States made the country's struggle an international issue of East-West confrontation. And they argue that when viewed as a percentage of national spending, Venezuela is giving a higher priority to its foreign aid program than the United States.

It is this aggressive international role, along with a recent souring of relations with Cuba, that has led the government here to embark on a program to modernize its military forces, officials here say. Venezuela has negotiated the purchase of six frigates from Italy for its Navy and French tanks for its Army.

Currently, Venezuela's Air Force is equipped mainly with French Mirages and British Canberra fighter-bombers, many of which were purchased in the early 1970s.

One high U.S. official here said that because of the impending sale of F16s, "it's possible that there would be other governments that would want them" in South America "and that we would sell." But other officials said the administration believes that requests for F16s from such countries as Argentina, Brazil, and Colombia are not likely now because of the planes' high cost.