House Republican leaders tentatively decided last night to postpone trying push through Congress $30 million in new aid for Nicaragua's contras that could be used to provide them with helicopters and airplanes.

Congressional sources said House Minority Leader Robert H. Michel (R-Ill.) and other key Republicans felt it would be better to wait for a more opportune moment to make a stand on contra aid rather than agree to the Reagan administration's request that they attempt to include the funds in a bill that would fund all government operations in the current fiscal year.

The sources said the decision was prompted primarily by the fact that dissatisfaction in the House Republican caucus over other aspects of the spending bill, known as a continuing resolution, is so strong that the Republicans believe they should work for its defeat. One Republican aide summed up the position by saying:

"As we see it, the bill is so bad we would be wasting a good effort for a good cause by including {contra aid} in a very bad bill."

In addition, other Capitol Hill sources noted that House Democrats, fearful that the request is part of an administration effort to circumvent the five-nation Central American peace process, appear to have more than enough votes to defeat a request for any kind of contra aid at this time.

At issue is the administration's argument that the $30 million is needed to sustain the contra forces through February, when it will be clearer whether the peace process is leading to democratization in Nicaragua. The administration has deferred until January its plans to request $270 million in new contra military aid, and the only aid currently available to the rebels is $3.2 million in humanitarian assistance that technically expires Dec. 16.

In recent days, administration officials led by President Reagan's new national security adviser, Lt. Gen. Collin L. Powell, have sought to convince key members of Congress that the aid should be voted as an "insurance policy" to keep the contras viable if the peace process breaks down.

However, the administration's request for what it calls "nonlethal aid" touched off alarm bells among Democrats, who claim that it goes far beyond what the contras need in basic humanitarian assistance. Instead, the Democrats charge, the administration plans to use most of the money for helicopters, airplanes and electronic protection equipment that would allow the contras to widen significantly their guerrilla war against Nicaragua's Marxist Sandinista government.

In the Democrats' response last Saturday to President Reagan's weekly radio address, Rep. Tony Coelho (Calif.), the majority whip, charged that the administration wanted the money "to step up the war" and said that Reagan should join House Speaker Jim Wright (D-Tex.), a strong supporter of the peace plan, by putting "the power and prestige of the Oval Office behind the drive for peace in Central America."

House Democrats contend that the administration, aware that it cannot get Congress to vote additional military aid for the contras, has adopted the "nonlethal" terminology as a means of getting military-related equipment and training that will expand the contras' fighting capacity. Rep. David E. Bonior (D-Mich.) said the funds would enable the contras to "double the size of their air force," and other Democratic members pointed out that Defense Secretary Frank C. Carlucci acknowledged Monday that much of the money would be used for electronic countermeasures equipment to protect contra aircraft.

Congressional sources said that the Republican leadership, in response to the administration request, initially considered a bid for $16.5 million in contra logistical support and $14.5 million for "transportation," which would include the aircraft acquisitions.

However, the sources said, as the extent of the Democratic opposition became clear, the Republicans also considered cutting their request by as much as half in hopes of winning over some Democrats. The sources noted that these same choices still will face the Republicans if they elect to seek the contra aid by trying to include it in some other legislative vehicle in the House or Senate, where it also faces strong Democratic opposition.