President Reagan refused yesterday to discuss U.S. military options in El Salvador or to say whether he has authorized covert operations to destabilize the government of Nicaragua.

At his news conference in the East Room the president repeatedly declined to give direct answers to a series of foreign policy questions, most of them about U.S. policy in Central America or the Caribbean. Reagan said that it would not be in the "national security interest" for him to answer some of the questions. He said he would address some of the questions in a speech next week to the Organization of American States in Washington.

Administration sources said that Reagan in that speech would propose an additional $300 million in Caribbean assistance, most of it economic, plus a preferential price mechanism for the important regional export of sugar. These sources said that Secretary of State Alexander M. Haig Jr. also was urging strongly worded presidential rhetoric directed at Cuban activities in the hemisphere.

The Washington Post reported Sunday that the president has authorized a broad program of U.S. action in Central America including encouragement of political and paramilitary operations against the Cuban presence in Nicaragua.

Reagan gave these answers yesterday to questions about U.S. foreign policy:

* Said "there are no plans to send American combat troops into action anyplace in the world" but declined to respond to a question asking how far he was willing to go to keep the Duarte government in power in El Salvador. Reagan said that it was wrong to "put down specific do's or don't's in such circumstances."

* Refused, in response to a related question, to say whether there was any "secret plan" for American involvement in El Salvador.

* Said that U.S. policy toward Cuba and the Caribbean was "under review and discussion" and on this basis declined to say whether the Soviets were violating the 1962 agreement with President Kennedy prohibiting the introduction of offensive weapons into Cuba. Reagan did say that Soviet arms flowing into Cuba had reached a greater tonnage than at any time since the Cuban missile crisis and that Cuban arms were finding their way to Nicaragua.

* Said that he had reached no decision on whether the United States should again bail out the Polish government by making the interest payments on Polish debts. But the president vigorously defended the U.S. action in paying the last installment of interest payments, saying that "in doing that, we retained our leverage because default would mean great financial hardship for a great many people and a great many institutions here in the West."

* Declared that reports about new arms sales to Jordan in the wake of Secretary of Defense Caspar W. Weinberger's trip to the Middle East were "overblown." Reagan said there had not been a request for additional arms and no change in U.S. policy toward Israel, the same point he made Tuesday in a letter to Israeli Prime Minister Menachem Begin.

For the most part, Reagan seemed more in command yesterday on foreign policy issues than he has at some press conferences, perhaps because he declined to go into detail on most of the questions. It was a tactic he followed frequently at his press conferences when he was governor of California and one that some of his advisers have urged on him as president.

The president had a shaky moment, however, when the third question of his press conference raised the question about covert U.S. activities in Nicaragua. The first question had been about El Salvador. When Reagan was asked whether he had approved covert activities in Nicaragua, he replied:

"No, we're supporting them. Oh, wait a minute, wait a minute. I was thinking El Salvador because of the previous [question]. . . . Here again is something upon which because of the national security question I will not comment."