Reagan administration officials yesterday predicted that the House would approve President Reagan's proposal for a $100 million aid package for the Nicaraguan rebels. While at least two key Democratic members of Congress agreed with this estimate, House Majority Whip Thomas S. Foley (D-Wash.) said that he has "every confidence" that the measure will be defeated.

Reagan stepped up his lobbying with phone calls to House members, as both sides maneuvered for what one administration official called "the psychological advantage of appearing to be on the winning side" before Thursday's vote. They agreed that the outcome will be decided by a narrow margin, perhaps by fewer than a dozen votes.

Meanwhile, Pentagon officials said the United States may help the rebels, known as contras, or counterrevolutionaries, buy Soviet SA7 antiaircraft missiles on the black market if Congress approves the package, which contains $70 million in military aid and $30 million in humanitarian assistance. The weapons would be used against Soviet-made helicopters operated by Sandinista pilots, which have proved effective against the contras.

A Pentagon official involved with drafting the assistance package said that the U.S. counterpart to the SA7, the General Dynamics shoulder-fired Redeye missile, also could be purchased if the aid package is approved.

According to government sources, the Central Intelligence Agency has provided funds to buy the battle-tested SA7 antiaircraft missiles on the world market for the Afghan rebels to help them counter Soviet helicopters there.

The White House had no comment on what weapons systems would be furnished the contras. Instead, administration officials tried to build support for the aid proposal by distributing polls, some from last June, showing that an overwhelming majority of the people in Honduras, Costa Rica, Guatemala and El Salvador support aid to the contras.

The surveys, commissioned by the U.S. Information Agency and taken by the Gallup affiliate in Central America, were described as "perfectly authentic" by Philip C. Habib, the president's special envoy to Central America.

However, a report on National Public Radio's "All Things Considered" on March 7 said that a survey showing 69 percent approval for aid in Costa Rica, the figure released yesterday at the State Department, was taken last July after a bloody border clash involving Sandinista forces. Only 39 percent of Costa Ricans approved aid in a subsequent November poll that was not released, according to the report.

White House deputy press secretary Edward P. Djerejian said last night that a survey taken in February on U.S. aid to the contras showed a 50-11 percent approval in Costa Rica and a 57-10 percent margin in Honduras. He said those polled had at least one year of secondary education.

Reagan claimed yesterday that the surveys showed "over 90 percent of the people" in some Central American countries support assistance to the contras. White House officials said the leaders in these countries also support assistance but are reluctant to do so publicly until they know what Congress will do. Reagan met yesterday with Habib, who returned to Washington after talks in Central America that White House spokesman Larry Speakes called "very productive." Habib is expected to return to the region after Congress votes on the aid package.

Senate Majority Leader Robert J. Dole (R-Kan.) said yesterday that he plans to bring the package up in the Senate Friday or Monday and said it could pass without amendments. Sen. Bill Bradley (D-N.J.) also predicted that the measure will pass the Senate.

But the tougher hurdle, both sides agree, is the Democratic-controlled House, where opinions were split along partisan lines yesterday about the impact of the president's nationally televised appeal Sunday for military assistance to the rebels. Foley said that opponents of the plan had lost one vote and gained one and would win Thursday by a "not overwhelming but conclusive" margin.

Two other Democrats said privately in separate interviews that momentum was clearly on the administration's side on the issue and that the president had been helped by the speech. Vice President Bush said on NBC's "Today" show that the House would approve the package.

Administration sources said that four Democrats led by Rep. Ike Skelton (D-Mo.) could hold the key to the outcome. Skelton last week sent Reagan a letter offering to provide immediate aid, including such defensive weapons as the shoulder-fired antiaircraft missiles, to the contras but withholding offensive weapons for 90 days pending further diplomatic negotiations aimed at convincing the Sandinistas to bargain with the contras.

Reagan has not replied to the letter. A White House official said the administration is waiting to see whether a partial delay in aid is necessary as a condition of winning the the House vote.