For both supporters and opponents of reform in the Soviet Union, the summit is a sideshow. Watching journalists set up their computers and cameras in the 1,000-capacity summit press center, a Soviet Communist Party official talked of the ``real political struggle'' that is pitting reformers against conservative party leaders. The struggle has intensified in recent months, with the approach of the nationwide party conference scheduled for the end of June.
The party official, a staff member of the Central Committee, noted that an attempt to derail the reforms in April had been beaten back. But, he predicted, opponents of the policies would probably try to strike again.
Some of the officials who have accompanied President Reagan to Moscow say that Mikhail Gorbachev is in firm command of the situation. Many Soviet observers see a precarious balance of power between Mr. Gorbachev and more-conservative leaders, headed by Yegor Ligachev, the official No. 2 man in the Soviet leadership. President Reagan will be meeting some of the most outspoken supporters of perestroika (restructuring) in two meetings today.
In the morning, he addresses a group of writers and intellectuals, many of whom have been in the forefront of change. In the afternoon, he is due to talk to students and faculty of the Moscow State University, the alma mater of Gorbachev and a number of other reform-minded leaders.
One United States official commented that Gorbachev's failure so far to move against conservative leaders was simply an effort to avoid jarring notes on the eve of the summit. Many Soviets, on the other hand, feel that resistance to reform is strong and well organized.
The last few days have seen intense activity in domestic politics. Last week, as US officials in the presidential advance party were briefing reporters, the official Soviet media published the ``theses'' - essentially the outline agenda - for the June party conference.
The theses made a number of important political proposals: limiting party or government office in most cases to two 5-year terms and cutting back party interference in administration.
A senior US official commented that the theses indicated that Gorbachev was in firm command of the situation. But supporters of reform expressed disappointment with the documents.
``They're a clear concession to the bureaucratic conservatives,'' one prominent activist said.
Others worry that the theses are phrased much too generally. ``Only the most tightly phrased instructions are ever implemented,'' the Central Committee official commented.
Several of the most prominent supporters of change have been rejected as conference delegates by party organizations. In retaliation, some have called for the conference to be postponed. Their call has apparently been ignored, and some of them are now saying that the conference will not produce the hoped-for breakthrough in reform.
The last days before the summit also saw a revolt in the country's normally compliant parliament, the Supreme Soviet. The revolt was clearly linked to the battle for change. Members of the Supreme Soviet contested, blocked, and finally defeated an official proposal for punitive taxation on private cooperatives.
In the view of reformers, the taxes would have crippled the effort to broaden the role of private enterprise in the Soviet economy. Some reformers view the planned taxes as a deliberate effort to do so. They also note the similarity between last week's proposal and a July 1986 law aimed at punishing unearned incomes. The law was quickly criticized by reform-minded economists, and has since been described as the first attempt to sabotage perestroika. Mr. Ligachev is said to have been a strong supporter of the law.
Other indications of domestic political ferment surfaced in the buildup to the summit:
In Moscow Saturday, a group demonstrated in support of Gorbachev's reforms.
In Leningrad, several thousand people are reported to have demonstrated for something not even radical reformers have called for: a multiparty political system.
Reuters reports that former Moscow party chief Boris Yeltsin, dismissed from his post last November after criticizing the Soviet leadership over the pace of reform, called Monday for the replacement of Ligachev.