President Reagan said yesterday that "the majority" of a new aid package for the Nicaraguan contras that he will seek from Congress will be "nonlethal" assistance, and a senior administration official said the request is likely to be "in the ballpark of $50 million."

An official familiar with administration deliberations on the package said that only about 10 percent of the request would be for weapons and ammunition but that the nonlethal portion of the aid includes funds for such items as helicopters and spare parts.

The official said the main purpose of the aid request would be to "keep the contras in the field, in existence" for several months to see if the leftist Sandinista government of Nicaragua proceeds with steps toward democratization.

The president acknowledged in a White House speech to contra supporters that the Sandinistas had made concessions, but he contended that "it's clear that it's the freedom fighters and only the freedom fighters that have brought the Sandinistas to the negotiating table and have wrung from them the limited reforms they've made."

The Sandinistas on Tuesday officially ended a six-year state of emergency in Nicaragua that had given the government extraordinary powers in dealing with political and news media opposition.

Reagan heaped scorn on Nicaraguan President Daniel Ortega, saying he repeatedly broke promises and had sought to create "a Soviet base camp in Central America."

While the president and other White House officials were stepping up their rhetoric against the Sandinistas and Democrats who oppose further contra aid, the administration was scaling down the aid request that the president plans to submit to Congress Tuesday.

Administration officials, talking last week about an aid package of as much as $100 million, said Reagan instead will make a request that one official described as "more modest and realistic."

This official said the precise amount of the package has not been set but probably would be announced Monday, when Reagan is to give his State of the Union address.

Officials who discussed the aid request on condition they not be identified said the lower figure is likely to be more palatable to Congress.

They said that because the contras, who have scored recent military successes, were given a significant amount of weapons last year, the present military effort could be maintained with reduced funding.

Under a compromise reached with Congress last month, the aid request cannot be amended but must be voted up or dowm by each chamber by Feb. 4. If the request is successful, Reagan could seek more funds for the contras in six months under a similarly expedited procedure.

The term "nonlethal aid" was introduced by the administration late last year in what Democratic foes of contra aid called an effort to partially circumvent a ban on supplying weapons to the contras.

The term used previously, "humanitarian aid," was understood to apply strictly to items such as food, clothing and medicine that guerrillas needed for day-to-day survival.

Administration officials have acknowledged privately that they deliberately substituted the phrase "nonlethal aid" to create a looser definition that would permit providing the contras with items such as helicopters and military training such as instruction in communications and equipment maintenance.

While Reagan was denouncing the Sandinistas, his spokesman Marlin Fitzwater was accusing Sen. Christopher J. Dodd (D-Conn.), an outspoken foe of contra aid, of "surrender" to the Sandinistas.

"The Democrats, Chris Dodd and others -- they want a surrender, and they think surrender is the best way to achieve peace," Fitzwater said at the daily White House briefing. "We disagree."

When a reporter asked Fitzwater if he was "redbaiting," the spokesman repeated his criticism of Dodd.

"I mean, he was all over television last night saying we just don't want peace and we don't want the peace plan," Fitzwater said. "That's outrageous and it's not true, and I'm not going to stand for it."

Dodd said Fitzwater's remarks were "typical, classic administration politics: When you can't win on the merits, attack somebody."

Staff writer John M. Goshko contributed to this report.