Nicaraguan authorities say the "menacing" language used by leading U.S. officials to denounce the construction of a military airport here only proves the need to continue building Nicaragua's military might against the threat of U.S. aggression.

Meanwhile, some diplomats here defend the government's right to build the airport, while others say the project and the government's talk of importing combat planes can only lead to a serious escalation of the Central American conflict.

President Reagan, Secretary of State George P. Shultz and other U.S. officials have condemned the construction of a new military airport by the Sandinistas at Punta Huete, 13 miles outside Managua.

Pentagon officials have called the new airport a potential Soviet base that could someday present a threat to the United States and endanger U.S. sea lanes in the Pacific.

One official recently evoked the Cuban missile crisis of 1962 and the building of a similar airport on the island of Grenada that led to U.S. intervention there last October.

"This project is on the threshold of becoming a serious concern," he said. "It is beginning to meet the requirements of those people who worry about the security of the United States."

The government insists that the base will be a defensive installation and have called U.S. fears of a Soviet base "absurd."

Sandinista officials recently took journalists to the site, where they said a 13,000-foot runway would be built that will be capable of landing any kind of aircraft, military or civilian.

The reason for the press tour, said the Sandinistas, was to "demystify" the $30 million project, which had been off limits to journalists since construction began in 1981, and to try to stem comparisons like the one with Grenada.

Nicaraguan Air Force commander Raul Venerio said the airport would be primarily military but would be used only to defend Nicaragua from attack. He said the base would also serve as an alternate civilian airport.

One of the most frequent questions about the base has been who is building it. When the Reagan administration approved U.S. military intervention in Grenada in Oct. 25, it said Cuban construction teams working on that airport project were actually military units and that the island was becoming a Cuban base and potentially a Soviet base.

Late last month, Army spokeswoman Capt. Rosa Pasos said Cuban engineers had advised the Sandinistas on the construction of the airport, but she denied that the Cuban military was involved in the project.

The Sandinistas also argue that the U.S. military is busy building and lengthening airstrips all over neighboring Honduras and that they are only keeping pace by building their base at Punta Huete.

Capt. Pasos and other officials have called the U.S. reaction to the new base "menacing."

The alleged threat of U.S. aggression is also one of the main reasons the Sandinistas say they are shopping around for sophisticated combat planes to use at the new airport.

Junta leader Daniel Ortega has said Nicaragua is interested in obtaining Soviet MiGs or French Mirages, although diplomats here agree the French will not sell combat planes to the Sandinistas.

The possible arrival of MiGs on Nicaraguan soil is another issue that has brought a strong reaction from the Reagan administration. U.S. officials say MiGs would give Nicaragua a marked air superiority in Central America and that the United States would not sit still for it.

The Sandinistas insist they must also build an air force comparable to that of Honduras. According to U.S. Embassy figures in the two countries, the Sandinista Air Force has three 1950s vintage jets, while the Hondurans are equipped with 12 French Super-Mysteres and 12 U.S.-made A37B Dragonfly bombers.

Diplomats based in Managua have known about the construction of the base for some time, despite the official secrecy surrounding it. Not all diplomats find the base as ominous as some U.S. officials in Washington do.

"So far it is just an airport," said one envoy. "The airport they have isn't very good and they are building a new one. That is their right, to build an airport anywhere in their country they please."

But other diplomats do share the U.S. concern over the base, especially with the Sandinistas' talk of importing combat planes.

U.S. officials have said for some time that there are MiGs waiting in Cuba for shipment to Nicaragua, and Sandinista officials have admitted that Nicaraguans are being trained in other countries to fly the combat planes.

But diplomats point out that because of contract clauses regarding third-party sale of the planes, no matter where the MiGs might come from the Soviet Union would have to give its approval.

"That will be decided by someone in the Politburo," said one diplomat. Most diplomats consulted expressed doubts that the Soviets would approve such a shipment any time soon, given the possibility that it might provoke the United States into action against the Sandinistas.

There are also doubts that the Sandinistas are serious about wanting MiGs in the country unless they are absolutely necessary. They have been talking about planes for some time, but with suggestions in U.S. government circles that the United States might even consider a preemptive strike against MiGs in Nicaragua, the move would seem counterproductive.

"The U.S. could come down here and take out that airfield and those planes without much trouble," said one diplomat. "That is something I'm sure everyone involved realizes."