The United States must "find a way" to help other countries fight off Soviet surrogate forces like the Cuban troops deployed in Africa, Defense Secretary Harold Brown said yesterday.

Acknowledging it is "not likely" that the United States would choose to send American troops to fight Soviet mercenaries directly, the Defense secretary contended that "we can help" people "trying to save themselves" from communist domination.

Brown's remarks before the House Appropriations defense subcommittee appeared to signal that the Carter administration is preparing to step up military assistance in crucial areas of the Mideast and Africa.

The defense secretary leaves tomorrow for talks in Saudi Arabia, Jordan, Israel and Egypt. How to combat Soviet surrogate forces will be at the top of the agenda, according to Pentagon officials, as Brown meets with foreign leaders and defense officials in those countries.

Lt. Gen. Ernest Graves, who directed the Pentagon's arms sales program, will accompany Brown on his swing from Feb. 9 to Feb. 19. The Pentagon team is expected to come back with several requests for new sales of weapons.

Under the Carter administration rationale, which Brown began to describe yesterday before the House subcommittee, the United States and Saudi Arabia are preparing to give jointly more than $200 million to North Yemen to combat Soviet-backed forces in South Yemen.

Such assistance, if extended as planned, is slated to be followed by other arms packages as President Carter moves to combat surrogate forces without committing American troops.

The Joint Chiefs of Staff, concerned about the muscle-bound nature of the nation's nuclear and conventional forces when it comes to the struggles being waged in the Third World, have commissioned a number of studies on how Communist surrogate forces could be combatted.

"We have not found an offset" for forces financed or otherwise encouraged by the Soviets to dominate developing countries, Brown told the subcommittee yesterday. His remarks could well be the opening argument for giving Third World countries specialized arms and military advice to fight off communist domination.

Brown's contention that "we have to find a way" to help people fighting for their survival against communist takeovers came in response to a complaint from Rep. Jack Edwards (R-Ala.) that the Soviets are making gains all over the Third World while "we're living in the shadow of Vietnam" and are "frightened to death about becoming involved."

Edwards ticked off a list of countries where he contended the Soviets, through their surrogates, are making significant gains: Afghanistan, Vietnam, Cambodia, Ethiopia and South Yemen.

While agreeing that the communist surrogate forces are indeed threatening U.S. interests in a number of nations, Brown said that "there is another side" to the gloomy picture Edwards painted.

"I'm sure the Soviets are asking themselves," said Brown, "'How did we lose China and Japan?'"

The defense secretary said that the strengthened ties the United States is developing with the People's Republic of China and the Sino-Japanese friendship treaty are significant gains from the U.S. standpoint. He said further that there were developments favorable to the West in Portugal, Spain, Egypt and Nigeria.

The Soviets have lost standing in Egypt and now have looser ties than before with Syria and Iraq, Brown maintained.

The bright side of the picture, Brown acknowledged "doesn't save us from our dependence on Mideast oil" nor offset the risks in Iran. However, Brown said, "It does show the picture is mixed. We win in some areas, and we lose in some areas."