The first non-emergency U.S. aid to Nicaragua's new Sandinsta-led government, nearly $9 million in economic assistance and limited military training, was approved 7 to 3 by a House subcommittee yesterday following strong State Department pleas not to "walk away" and "turn our backs" on that country.

Deputy Secretary of State Warren Christopher told the House Appropriations subcommittee on foreign operations that "the current situation in Nicaragua presents a critical challenge and a major opportunity" for U.S. foreign policy.

"We recognize that some elements of the present government might prefer a closed, Marxist society," Christopher testified. But "the moderate outcome we seek will not come about if we walk away now."

Members of Congress have expressed strong concern that the Sandinistas, who took power July 20 after leading a two-month civil war that ousted the 45-year Somoza dictatorship, will turn far to the left and follow a Cuban revolutionary model.

Last week, the House of Representatives defeated, 221 to 189, an amendment proposed by Rep. Robert Bauman (R-Md.) to the administration's 1980 aid requests that would have banned assistance to Nicaragua until Congress could determine if the country would become "another Cuba."

The money authorized yesterday was from unused portions of the 1979 aid budget for other countries. It was held up for more than a month when subcommittee chairman Rep. Clarence Long (D-Md.) called for hearings.

Although the administration uas not required to seek renewed congressional approval for the funds, sources said they submitted the request to the subcommittee out of recognition of congressional concern over the Nicaraguan situation.

The bulk of the funds, $8.8 million, will go for reconstruction and price stabilization in the war-shattered economy.

Perhaps more important in symbolic terms, however, is a small $23,600 military training grant that will send 20 Sandinista soldiers for several weeks to U.S. bases in Panama, and two Sandinista commanders on a tour of military bases in the United States.

The grant will result in friendly contact between the U.S. military and the Sandinista National Liberation Front's army after the antagonism based on historic U.S. support for the Somoza government.

The Sandinistas have said they will request extensive U.S. military assistance in the future, and have asked for "massive" economic aid for immediate reconstruction and relief needs.

The State Department views the Nicaraguan case as an "important symbol" of U.S. ability to respond to revolutionary change in Latin America.

Since a five-member Sandinista-appointed junta took power following former president Anastasio Somoza's resignation in July, both countries have been watching each other nervously. For the Sandinistas, the United States is a traditional enemy that supported Somoza long after most of the rest of the world rejected him, and actively worked against their takeover.

For the United States, the Sandinistas are a relatively unknown quantity who look like, and sometimes talk like, the Cuban revolutionaries who have complicated U.S. policy in Latin America -- and more recently Africa.

But the State Department apparently has become convinced, that, as Christopher said, the best way to promote democracy in Nicaragua is to "work with the new government."

While Christopher said that "lines of authority within the government are still unclear and there is considerable administrative confusion," the junta and a 19-member Cabinet "include many moderate leaders."

"The government's orientation, as revealed in its initial policies," Christopher testified, "has been generally moderate and pluralistic, and not Marxist or Cuban. The government has restrained reprisals" against Somoza's National Guard, "-- indeed, I believe it has been more successful in doing so than any other recent government which has come to power in the wake of a violent revolution."

"Without adequate support for reconstruction," Christopher said, "the Nicaraguan government might resort to authoritarian measures to expedite economic recovery"

Christopher and other witnesses before the subcommittee noted that the Cuban government has already offered economic assistance to the Nicaraguans.

In answer to subcommittee questioning on how the United States would judge Sandinsta performance in the future, U.S. Ambassador to Nicaragua Lawrence Pezzullo said he would be watching for observance of human rights, political freedoms and freedom of expression and "attitude toward the United States."

he subcommittee also conducted a one-hour closed session to hear testimony from the Defense Intelligence Agency and the Central Intelligence Agency. Long said he would ask whether "Nicaragua was in danger of coming under the dominance Cuba," and if the Nicaraguan revolution threatened other conservative Central American governments.

The subcommittee also heard testimony from Luis Pallais, a member of the Somoza government who has sought political asylum in the United States. Pallais said that "the Sandinista strategy [is] to mask their true objectives" of turning Nicaragua into a Marxist society because of Nicaragua's "great need of economic support from the capitalist world."

In a concurrent hearing of the House Foreign Affairs subcommittee on Inter-American affairs, Viron P. Vaky, Assistant Secretary of State for Latin America, said that while "the impact of recent events in Nicaragua is assuredly a factor in the internal politics of all countries in Central America . . . even without Nicaragua the situation would be volatile."