The first delegation of religious leaders allowed out of China in more than 25 years insisted here this week that Peking now is implementing the religious freedom provision of the Chinese constitution.

Christian, Buddhist and Moslem representatives, in the United States for a World Conference on Religion and Peace, spoke of the "rehabilitation" and "development" of religion in China since the fall of the "Gang of Four" three years ago.

Speaking at a press conference at the China Mission to the United Nations, they told of steps to reopen churches, temples and mosques closed during the cultural revolution. They contended that the number of religious believers today is approximately the same as a generation ago.

Bishop Ding Guangxun, a Protestant, disclosed plans for a revised edition of the Chinese New Testament to be published with official approval in 1980 or 1981. He also said interreligious efforts are under way inside the People's Republic to persuade the Communist government to revise a constitutional article sometimes "misunderstood" as favoring atheism over religious faith.

Chou Puchu, acting president of the Buddhist Association of China, noted that the recent Fifth National People's Congress approved sentences of up to two years in prison for government workers who violate the religious freedom policy.

Chou, a layman and poet, and Bishop Ding, an Anglican who does not use his ecclesiastical title in China, are members of the People's Congress, which in theory is China's highest political authority. They were joined at the press conference by Li Shoubao, a lay official of the YMCA in China, and Imam Hadji Yang Pinsan of Peking's Dongsi Mosque.

The four are part of a nine-man Chinese delegation to the Third Assembly of the World Conference on Religion and Peace (WCRP), meeting at Princton Theological Seminary Aug. 29 through Sept. 7, WCRP sponsored the press conference.

The presence of Chinese participants at an international religious meeting may itself signal a changing attitude toward religion in post-Mao China. Even before the outbreak of the cultural revolution in 1966, religious leaders from the mainland were noticeably absent from world ecumenical and interreligious gatherings.

Negotiations that brought the four Christians, three Buddhists and two Moslems to the Princeton meeting took place over a period of several years. The World Conference on Religion and Peace was unsuccessful in arranging Chinese participation at its assemblies in 1970 and 1974. China has an estimated 100 million Buddhist, 10 million Moslems, 3 million Roman Catholics and 700,000 Protestants, according to the delegation. Asked why no Catholics were included, a delegation member replied, "The Roman Catholics decided not to come."

Chinese Catholicism has had no relations with the Vatican for a quarter of a century, Pope John Paul II has called for reestablishing ties broken after China came under Communist domination.

In explaining what appears to be new respect in Peking for a religious liberty clause written into the 1954 Constitution of the People's Republic, Bishop Ding said:

"The Communists are not in favor of religion, but the building of socialism is a task that can't be monopolized by a single party or organization. The government needs to mobilize as many people as possible from all walks of life in building our country."

Bishop Ding and Li, both speaking English, denied that atheism enjoys greater constitutional sanction than religious faith in China, though they acknowledge a reason for such an impression.

In 1975, they said, the 1954 constitution's simple guarantee of religious freedom was expanded to assure the freedom not to believe. Article 46 of the constitution is worded in such a way, said the bishop, that it "misleads people to think only atheism can be promulgated."

"The article is not meant to prevent religionists from preaching religion," he said, "but the two freedoms [to believe or not believe] are not put in a balanced way. Sixteen religious leaders have written a proposal that the constitution be changed to its original wording, simply that all citizens have freedom of religion."

Freedom for organized religion in China has fluctuated since the Communist victory in 1949. Despite the constitutional guarantee of 1954, religion suffered setbacks during the cultural revolution and the ascendency of the Gang of Four, a fact stressed by the religious leaders visiting the U.S.

"The vicious Gang of Four brought about serious damages in all fields, and religion was certainly not exempted," Chou, head of the delegation said in a prepared statement.

Like houses of workshop, the YMCA's and YWCAs across China were closed by the culture revolution, and Li who spent those years advising students in Shanghai on international relations.

"After being suppressed, the Ys are being restored," he stated. Li also reported that several church buildings in Shanghai are being reopened for use by Chinese Christians. In recent years, most Christian worship has taken place in house-churches.

On the question of renewed ties between the Vatican and the Chinese Catholic Church, Bishop Ding said the problem has to do with the appointment of diocesan bishops. During the war years, he said, Rome refused to appoint new bishops to replace foreigners officially in office but physically absent. Bishop Ding stated:

"Chinese Roman Catholics began to elect and consecrate their own bishops without approval of the Vatican. A new bishop was recently elected in Peking. When the Catholic community in China needs a bishop, it produces one. The principle here is that the Chinese Church ought to be independent, with no interference in domestic life from the Vatican."