Reagan administration officials yesterday acknowledged that a number of Americans will endure pain and suffering when federal spending for social programs is cut next fall.

But they attempted to persuade a skeptical convention of the National Urban League here that the reductions are essential to strenghthen the economy and provide a surge in new employment.

Vernon Jordan called our policies a jellybean budget," Labor Secretary Raymond J. Donovan said. "Everyone knows that jellybeans are sweet, with no real substance. That hardly describes our programs." Derisive laughter and applause rippled across the convention hall.

Donovan and Housing and Urban Development Secretary Samuel R. Pierce Jr. said the cuts will cause some pain. Pierce said he believes, however, that people will adjust somehow and not be forced into the streets, homeless and hungry.

League President Jordan has had Vice President Bush and six members of the Cabinet speaking to his group's annual meeting here for what he has described as a debate over the Reagan administration's social economic policies.

But there was grumbling among a few league members yesterday that the debate had turned into an unchallenged forum for the administration's views. Only Pierce made himself available for questions after speaking.

When he was asked to describe his position on extending the Voting Rights Act, a major goal of the Urban League, however, Pierce responded, "I have a very definite position on it, but I want to argue that within the Cabinet." a