The U.S. Agency for International Development has decided to postpone allocation of $23 million for the U.N. Fund for Population Activities.

M. Peter McPherson, the AID administrator, said he had ordered "a careful review" of the assistance because of concerns expressed about China's population program by private groups and members of Congress and because of recent press articles on the subject. Other AID officials said the review would probably take several months.

McPherson's comment was made through a spokesman in response to a question from a reporter. Members of several private groups supporting family planning efforts have expressed concern that the $23 million is being held up, and McPherson confirmed that it is.

China would be the recipient of only a small portion -- and possibly even none -- of the $23 million in question. But questions raised about its family planning program have apparently cast doubts within the Reagan administration and the Congress on the United Nations program as a whole. The population fund has provided $50 million to China for its population program from 1980 through 1984.

The hold on money for the population fund reflects opposition of the right-to-life movement inside Congress as well as last year's shift within the Reagan administration away from U.S. government support for population programs. Administration officials have suggested that free-market economics and economic growth, rather than family planning, are the best means to limit the world's population and make its people more prosperous.

But officials of the U.N. Fund for Population Activities argue that their organization does not support programs relating to any form of coercive family planning and does not advocate abortion.

Nafis Sadik, the agency's assistant executive director in New York, said that the $23 million, if eventually approved, would go for voluntary activities related to family planning, such as education, training, and the provision of contraceptives.

In China, agency funds have been allocated to support the first census since 1964 and such items as training and research, education and communication programs, and family planning services, said Rafael Salas, the U.N. organization's executive director.

Sadik said that the Chinese had "taken important steps" to deal with reported abuses in their family planning program, such as forced abortions.

Werner Fornos, president of The Population Institute, a Washington-based private organization that supports population assistance to Third World nations, said in a prepared statement that, contrary to recent press reports, he found during three trips to China that leaders were "bending over backwards to make certain that their programs reflected a spirit of voluntarism."

Last year, AID held up a $19 million grant to the population fund until it received assurances from the agency that it was not supporting abortions.