Henry A. Kissinger returned to the State Department yesterday as architect of the Reagan administration's long-range strategy in Central America and said the newly created national commission on the region "will try to make its contribution to avoiding another Vietnam type of crisis."

"I think it is imperative that we avoid the bitter debates that characterized the Vietnam period, and also that we avoid the same kind of uncertainty about objectives and about what was attainable that characterized so much of the period," Kissinger said in a news conference at the department where he served as secretary of state during the Nixon and Ford administrations.

President Reagan last week named Kissinger, once his favorite target as a symbol of U.S. foreign-policy failures, to head the 12-member National Bipartisan Commission on Central America.

Kissinger yesterday said he took the post "with considerable reluctance after turning it down several times, when the president called me and said he had no second choice." Because he had served as secretary of state, Kissinger said, he felt he didn't have a right to refuse the president.

But others who are supporters of the controversial Kissinger, to whom Reagan referred as "almost a legend" in announcing his appointment, said the commission is a chance for Kissinger to return to the limelight in a constructive way.

Senate Majority Leader Howard H. Baker Jr. (R-Tenn.), who lunched with the president yesterday at the White House, complimented Reagan for making the appointment, and said that Kissinger was highly motivated to produce a long-term report that could chart Central American policy.

"I think that Henry certainly wants to succeed," Baker said. "I think he sees it as an opportunity to define a new role for himself, an opportunity for a former secretary of state to become a world diplomat."

On Sunday, Sen. Daniel Patrick Moynihan (D-N.Y.), vice chairman of the Senate Select Committee on Intelligence, was scornful of the commission concept, saying: "When has foreign policy been made by a commission? That's what you have a secretary of state and president for."

The point is a sensitive one to the White House and Kissinger, who at his news conference took pains to deny that he was in any way supplanting Secretary of State George P. Shultz in the formation of U.S. policy in Central America.

Before he was asked any questions, Kissinger announced that the commission's purpose was to make recommendations "about long-range and middle-range objectives in Central America" and that it would "not deal with current operational issues." Kissinger said the commission would report on Feb. 1, two months later than the deadline given by Reagan in his announcement, and said it would cease to function after it makes its recommendations.

"I am not taking over Central American policy," Kissinger said in response to a question.

Despite Kissinger's efforts to put distance between himself and current operations in Central America, administration officials predicted that he inevitably would become involved in current policy.

"He's always been available to give advice and it's reasonable to think he would continue to be," said one official.

Officials said that the commission would have so much work confronting it, however, even with the later deadline, that Kissinger's availability on day-to-day issues would be limited.

Kissinger was asked yesterday whether his "working premise" was that both the U.S.-backed government in El Salvador and the U.S.-opposed Sandinista regime in Nicaragua would still be in power when his commission reported.

"I think that's our premise, but if it isn't we'll have to think of another," Kissinger said with a smile. "If either of them isn't, we'll have to make another five-year projection."

The mandate of the commission is broad. Kissinger said the commission would outline "the political, economic, social and security goals" for the United States in Central America."

To accomplish its purposes, Kissinger said, the commission could be expected to visit the countries of the region, including Nicaragua, "if we are welcome."

He also responded to comments that the commission is insufficiently representative of critics of the administration's Central American policy by saying, "We will give every significant group of every point of view within the United States an opportunity to be heard . . . ."

It was like old times at the State Department yesterday when Kissinger returned. He was greeted by 18 television cameras, more than twice the number usually on hand for Shultz, who was nowhere in sight.

Kissinger also attracted a crowd of cameras at the White House yesterday morning when he arrived for a 20-minute meeting with the president. An official said Reagan gave his views at some length, including telling Kissinger he did not think Mexico should be part of the commission's study. At this meeting Kissinger told the president he thought the commission would need an extra two months to complete its work.

In a pre-arranged White House plan, Kissinger was spirited out through the adjoining Executive Office Building so photographers could not take his picture.

White House officials gave various explanations for this tactic. One said Reagan was aware of conservative hostility to Kissinger and wasn't anxious to emphasize his presence. Another said a Kissinger appearance before microphones and cameras at the White House "might suggest that he's somehow in charge of Central America."

Kissinger was fully in charge at his news conference. When a reporter said to him that the consensus among State Department correspondents was that the seventh floor, where the secretary of state has his office, would be "somewhere in orbit" if Shultz had been named to head a commission during Kissinger's tenure, Kissinger replied: ". . . The seventh floor tended to be in orbit anyway, with my boiling point."