The Pentagon announced yesterday that it will begin another large-scale exercise in Honduras next month, sending tanks there for the first time and deploying as many as 4,500 U.S. troops at once in that Central American country.

The exercise, Big Pine 3, is the fourth large maneuver the two nations have conducted in two years. Pentagon officials said it will last about three months, unusually long for a military maneuver.

Reagan administration officials have said that the Big Pine exercises are intended to bolster the Honduran military and intimidate the Sandinista government of neighboring Nicaragua, which U.S. officials have accused of having designs on Honduras.

The Hondurans agreed to Big Pine 3 despite earlier reports that some Honduran officers were eager to diminish the U.S. military presence in their country unless the United States guaranteed more aid and a security pact. About 1,500 U.S. military personnel are now stationed in Honduras between exercises.

Engineering companies participating in Big Pine 3 will improve runways and aprons at existing airfields at Cucuyagua, not far from the Salvadoran border, and San Lorenzo, near the Nicaraguan border. The engineers also will improve and extend tank obstacles along the only flat road between Nicaragua and Honduras.

The exercise, known as Ahuas Tara III in Miskito Indian language, also will include antitank training near San Lorenzo and antiguerrilla war games in Yoro province, north of the capital of Tegucigalpa. The maneuvers will last from Feb. 11 through April 12.

Michael I. Burch, chief Pentagon spokesman, said last fall that U.S. exercises in Honduras were intended to "remind" the Nicaraguans "that perhaps they should not have any designs on their neighbors."

Nicaraguan officials have denied any hostile intent toward Honduras or Costa Rica, saying that Washington uses the allegation to justify a military buildup in the region.

The Nicaraguans also have said that airstrips built during previous exercises have been used by CIA-backed "contra" rebels, who are trying to overthrow the Sandinista government from bases in eastern Honduras.

U.S. officials have responded that the exercises are not intended to aid the contras and that they cannot control who uses the airstrips once U.S. forces leave.

U.S. forces conducted an eight-day exercise in Honduras, known as Big Pine 1, in February 1983. Big Pine 2 extended from August 1983 until February 1984, and involved as many as 5,500 troops at a time.

Granadero 1 lasted from April through June last year. Since then, the military has conducted a series of smaller exercises, frequently unannounced and with more than half a dozen proceeding simultaneously.

The military also has installed radars, a hospital and other equipment that was sent to Honduras for the maneuvers but has remained there since. The Pentagon said yesterday that it has no plans to leave any equipment behind after Big Pine 3.

The Marines practiced amphibious tank landings in Honduras during Big Pine 2, but the military has not conducted any armor exercises inside the country until now. The Pentagon said that an undisclosed number of M60A3 tanks and M113 armored personnel carriers will be flown to Honduras for an "antiarmor field training exercise" from April 8 through April 13.

The exercise will begin with "a display of armored and mechanized vehicles at San Lorenzo," located in the narrow wedge of Honduras between El Salvador and Nicaragua, and will end with a "closing ceremony" on April 13.

"This is not a massing of armor, nor will it take place near the border," a Pentagon spokesman said. Pentagon officials have said that all exercises stay at least five miles from the Nicaraguan border.

The spokesman said Honduras will participate with its British-made Scorpion armored personnel carriers.

Big Pine 3 actually began with small map-reading and command exercises, intended to improve cooperation between officers of the two armies, from Dec. 10 to Dec. 14 and for five days last week, ending Friday.