President Reagan observed his seventh anniversary in the White House yesterday by proclaiming the success of what he called a "revolution" in domestic and foreign policy and by pledging to keep U.S. aid flowing to "freedom fighters" in Nicaragua and Afghanistan.

Speaking at Constitution Hall to an annual rally of his top appointees, the president appealed for "one more year, not for the Gipper but for Americans and for all mankind. As they say in show biz, let's bring them to their feet with our closing act."

In a speech that appeared to preview many of the themes of next Monday's State of the Union address, Reagan gave himself rave reviews for his performance during the last seven years, then returned to his familiar routine of saying U.S. military support for the Nicaraguan contras is the key to democratic progress in Central America.

"This is . . . the year that the United States will strongly affirm that democracy, not communism, is the future of Central America," said Reagan, who predicted that the leftist Sandinista government of Nicaragua would "institute democratic reforms" only if pressured to do so by the contras, whom the administration has supported since 1982.

A few hours later, the White House announced that the president had authorized resumption of air drops to the contras of previously stockpiled weapons and ammunition.

This previously authorized aid was suspended as part of a compromise last month with Congress. The money to pay for these weapons and for foodstuffs authorized as part of the compromise is expected to run out by the end of February unless Congress approves additional aid.

Reagan was equally forceful in calling for continued military aid to rebels in Afghanistan, an issue on which he has bipartisan support from many Democrats who oppose aid to the contras.

The Soviet Union has announced its intention to withdraw an estimated 115,000 troops from Afghanistan after eight years of occupation but has called upon the United States to cease providing military aid to the rebels when a withdrawal commences.

Reagan has refused to do this. He said in his speech "that the Soviet troops must leave Afghanistan, and the United States will never agree to any steps that would put the freedom fighters and Afghan hopes for self-determination at risk."

Reagan also vigorously defended his administration's domestic record, saying that low income tax rates and deregulation that he sponsored were responsible for "the great economic expansion of our country."

He denied that the appeal of these tax cuts, which have helped to produce a record federal budget deficit, was based on "greed" or "selfishness" and predicted that the economy will remain strong.

"The doomsayers, who can't make the front page or network news unless they've got something bad to say, have been wrong for the last seven years and, in 1988, we and the American people are going to prove them wrong again," Reagan said.

The president called upon the Senate to ratify the Intermediate-Range Nuclear Forces (INF) Treaty that he and Soviet leader Mikhail Gorbachev signed last month and for speedy confirmation of Supreme Court nominee Anthony M. Kennedy.

Reagan also asked Congress to approve the U.S.-Canadian free-trade agreement that he and Canadian Prime Minister Brian Mulroney signed Jan. 2.

Reagan said his policy of "standing firm" had brought the Soviets back to the bargaining table and produced the INF agreement. He appealed for congressional support for his Strategic Defense Initiative, saying, "I would hope that Congress does not, in the months ahead, take away in the committee room what the Soviets were unable to get at the bargaining table."

The president said he hopes for progress this year on a strategic nuclear arms reduction treaty with the Soviets but added that, "if we are to enter into a new period of rapprochement with our adversary," the Soviets must improve their human rights record and allow "a further opening of the emigration door."

White House officials said that the Reagan-Gorbachev summit in Moscow is being planned for sometime from mid-May through June 4 and that the president will attend a North Atlantic Treaty Organization summit in Brussels March 2-3.