Soviets and East bloc face reform struggle. Gorbachev's reforms are headed for trouble at next month's party conference, the first in 47 years. Hungary, a pioneer in reform, holds its own crucial party gathering today.

Soviet reformers fear that next month's Communist Party Conference, intended to rally support for far-reaching economic and political change, is running into trouble. Several of the most outspoken supporters of perestroika (restructuring) have failed to be selected for the conference. And there are complaints that the Communist Party apparatus - viewed as a main obstacle to change - dominates the process of selecting conference delegates.

One of the main tasks of the conference, the first to be held in 47 years, is to give a much-needed boost to the efforts of Communist Party leader Mikhail Gorbachev to reshape the Soviet Union. So far, reformers concede that these efforts have produced few tangible changes.

But some of the most prominent advocates of reform have already been rejected as delegates in the first round of the selection process. These include the economist Gavril Popov and the historian Yuri Afanasyev.

This was not what reform-minded Soviet leaders had in mind. In a speech published May 11, Mr. Gorbachev called for ``ardent'' supporters of reform to be selected for the party conference. But the selection of candidates has been entrusted to the regional party leadership - the group that will stand to lose many of its privileges if the party conference is successful.

``We must come to the conference with major proposals concerning [our] political system,'' Gorbachev said in his speech. He did not spell out these proposals, but reformers have called for the conference to discuss such issues as limiting the terms of senior party officials, more open party elections, and stricter oversight of party organizations.

Another major item on the conference agenda will probably be the need to sharply reduce the party's role in government. At the moment the party structure duplicates and usually dominates the governmental apparatus at all levels.

Reformers say that a reduction of the party's administrative functions will strengthen its role in ideological leadership. But it will also mean a considerable cutback in the size of the party bureaucracy, and the power of local party leaders.

At the moment, reformers say, regional party leaders can and do ignore instructions from Moscow. ``It takes the personal intervention of Gorbachev to remove a well-placed oblast [regional] first secretary,'' one reformer said.

Reformers feel that the onset of the conference was the reason behind an article which appeared in the central newspaper Sovietskaya Rossiya in March. The article was later officially denounced as part of an anti-reform political program. Some reformers say openly it was a plot against Gorbachev's leadership, supported by the second-ranking leader, Yegor Ligachev.

Response to the article provided eloquent proof of the vitality of opposition to reform:

Party committees throughout the country are reported to have discussed the article.

Thirty-four regional newspapers, many of them the mouthpieces of the regional party committee, reportedly reprinted it.

The official news agency Tass drew attention to it.

Only two newspapers apparently spoke out against the piece, and one is known to have refused to publish it.

The final selection of the 5,000 conference delegates will take place at plenary meetings of the regional or republican parties. So far, lower-level party organizations have met to suggest candidates. The plenary meetings are not obligated to accept the suggestions, officials say.

On Thursday evening students and faculty of Mr. Afanasyev's Institute of Historical Archives announced that they would challenge the district party committee that had rejected Afanasyev's candidacy.

But the reformers are less optimistic about results in other parts of the country. Reports in the Soviet news media recently expressed concern about elections in Odessa and Rostov in the south, and Omsk in Siberia.

And the party youth newspaper, Komsomolskaya Pravda, carried a report Tuesday describing the annual May Day parade in the Armenian capital, Yerevan. Among the banners carried by young marchers were ones reading, ``More democracy, glasnost [openness], light,'' and ``[Elect] honest communists for the party conference.'' They were told to take them down, the article reported.