The United States will put several thousand Marines and Army combat troops into Honduras as part of the series of military exercises that U.S. and Honduran forces will conduct in Central America during the next six months, senior Pentagon officials said yesterday.

As many as 4,000 U.S. military personnel may be in Honduras at any given time, the officials said, and many more could be involved during the course of the exercise. Some of them, forming a joint task force headquarters, will be in Honduras throughout the extended exercise, from August through January, the officials said.

The two Pentagon officials, who briefed reporters on condition that they not be identified, said the Marines will practice amphibious landings, and Navy carrier-based jets will conduct maneuvers off the coast of Central America, possibly over Honduras. They said Army engineers will build air strips in Honduras and may begin surveys for possible construction of a "naval facility" on its northern coast.

One of the officials said the exercises are intended to discourage the leftist Sandinista government of Nicaragua from behaving aggressively in the region. Responding to questioning, he said the exercises would be conducted "a sufficient distance" from the border between Honduras and Nicaragua "to avoid any problems."

After the Pentagon briefing, a senior official said troops from neighboring El Salvador might also be included in the exercises, although that would have to be worked out with Honduras.

The Reagan administration is aiding the government of El Salvador in its civil war with leftist rebels and is considering an increase in the number of U.S. military adivsers training government troops in El Salvador from 55 to as many as 125.

Yesterday's official confirmation of plans for a greatly increased and extended U.S. military presence in Central America through the land, sea and air exercises came as President Reagan scheduled a news conference tonight to discuss his policies in the region.

Reagan wants "an opportunity to put Central America in perspective" because the planned military moves there have been portrayed as "much more threatening than they are," a senior administration official said. "The president feels there has been too much emphasis on the militarization of policy in the region," the official said.

Democratic critics in Congress maintained that the president is putting too much emphasis on military means. They said the administration should cancel the planned exercises and seek to negotiate diplomatic solutions to conflicts in Nicaragua, where at least 10,000 U.S.-supported guerrillas are challenging the Sandinistas, and in El Salvador, where the U.S.-backed government is being challenged by about 5,000 leftist rebels.

Sen. Christopher J. Dodd (D-Conn.) yesterday requested an "urgent" meeting of the Senate Foreign Relations Committee to investigate whether to invoke the War Powers Act, which could give Congress an opportunity to veto the deployment of troops.

A spokesman for the committee chairman, Sen. Charles H. Percy (R-Ill.), said the panel will be briefed in closed session late this week by State and Defense Department officials, although not necessarily in response to Dodd's request.

Sen. Gary Hart (Colo.), a Democratic presidential candidate, said yesterday that many middle-level officers in the Pentagon feel "real concern" that the United States is headed for a conflict in Central America without popular support. Hart told reporters during a breakfast interview that many captains and colonels have been approaching members of Congress with those fears recently.

The House of Representatives prepared to debate an amendment today that would eliminate covert U.S. aid to the anti-Sandinista rebels in Nicaragua, while the administration is reported to be increasing support.

Asked whether the U.S. military maneuvers would encourage the "contras" seeking to overthrow the Sandinista government, a senior Pentagon official said, "That was not the purpose of these exercises."

The past week of events surrounding Central America has featured both peace offers and plans for military buildup. A leader of the Nicaraguan regime offered last Tuesday to participate in regional peace talks, and Reagan hailed that offer as a welcome first step.

At about the same time, the Navy dispatched the carrier USS Ranger with its eight-ship battle group with 70 jet fighters to the Pacific coast of Central America. Officials confirmed yesterday that the battle group is now operating about 100 miles off the coast of El Salvador.

In addition, Pentagon officials said Defense Secretary Caspar W. Weinberger had recommended increasing the contingent of U.S. military advisers in El Salvador from 55 to 125. White House spokesman Larry Speakes yesterday denied that such a recommendation has reached the president, although he said the situation is constantly under review.

During the weekend, administration officials said the United States was out to "modify" Nicaraguan behavior at home and abroad, and hinted that the United States might seek to impose a naval quarantine around Nicaragua to keep Soviet and Cuban weapons out.

Pentagon officials confirmed yesterday that a second carrier, the USS Coral Sea, will exercise off the Caribbean coast of Central America with its battle group when it returns next month from the Mediterranean. They also confirmed that the battleship USS New Jersey, reportedly traveling with five other ships, is steaming from Asia for the Pacific coast for similar maneuvers.

The officials said each of those carrier groups will spend two weeks or so in the area and then move on. They said "there is no plan for stopping shipments in international waters." But they would not say whether the ships would practice blockade maneuvers.

"They're doing all types of traditional training exercises and various scenarios," one official said.

Much about the six-month exercise remained sketchy, in part because Pentagon officials have yet to formulate detailed plans. This appeared to fit reports that the impetus for, and timing of, the exercises have emanated from the White House, with the Joint Chiefs of Staff scrambling to come up with workable plans.

"There are a lot of things that have not been worked out," a senior Pentagon official said. "Those things are usually laid out two or three years ahead."

Officials said a group of top military officials began meeting yesterday at the U.S. Southern Command in Panama to work out details of the long exercise, which will be called Ahuas Tara II (Big Pine, in the language of Central America's Miskito Indians). The chairman of the Joint Chiefs of Staff, Gen. John W. Vessey Jr., is scheduled to visit Honduras and Panama today, and a U.S. military survey team is to arrive in Honduras on Aug. 1.

Officials said the joint exercise with Honduran troops is likely to begin with a series of training sessions in artillery and other skills lasting a few weeks each and involving a few hundred American personnel. Those training sessions will culminate in one or more complex exercises involving 3,000 to 4,000 U.S. military personnel.

Officials said Ahuas Tara II will bring Marines and Army combat troops to Honduras for the first time for major exercises, not counting the combat engineers who participated in the much smaller Ahuas Tara I in February.

The purpose, a senior Pentagon official said, is "to give confidence to the Hondurans, to show they are not alone and to develop a shield so that aggression is deterred."

The official said that, if fired upon, American forces will follow the "standard practice rules of engagement: the commander has the authority to defend his unit."