Yeltsin Is Conciliatory on New Constitution : Russia: His special assembly appears too unwieldy. The June 16 deadline may be extended.

MOSCOW — Russian President Boris N. Yeltsin admitted Thursday that winning the endorsement of a handpicked assembly for his proposed constitution is proving harder than was expected, and he offered to give equal attention to a rival draft that would grant the less power to the presidency.

Yeltsin’s 10-minute speech to the constitutional assembly’s 700 delegates was far more conciliatory than his opening address Saturday, when his chief critic was shouted down by Yeltsin supporters and stalked out of the Kremlin’s Marble Hall.

But the president failed in an effort to woo that critic, Parliament Chairman Ruslan I. Khasbulatov, back to the forum. Offered another chance to speak Thursday, Khasbulatov called in sick. His absence further clouds Yeltsin’s campaign to purge Russia of its Soviet-era institutions and hold new parliamentary elections this year.

Yeltsin, who became Russia’s first democratically elected leader two years ago, has put top priority now on rewriting its basic law, a holdover from the 1970s and the Soviet era that gives supreme power to the Congress of People’s Deputies, now led by Khasbulatov.

Seeking to bypass the Communist-dominated Congress, Yeltsin summoned delegates from each of Russia’s 89 geographical subdivisions as well as from political parties, industrial enterprises, student groups, labor unions and religious congregations, a body meant to be more representative of the new Russia.

This week, however, it became clear that the conflicting interests of its parts make the assembly too unwieldy to accomplish its work by the June 16 deadline that Yeltsin set.

In his speech Thursday, the 62-year-old president acknowledged “differences are already arising” that the assembly’s drafting commission “will not be able to resolve.” He suggested for the first time that the forum remain in session after June 16. Other aides said it should adjourn then and reconvene as often as necessary.

Yeltsin’s draft calls for a strong presidency with the power to dissolve Parliament and enforce Western-style human rights and private property guarantees. It would also preserve Russia’s makeup as a patchwork federation of autonomous ethnic republics and less independent regions.

The proposal has met opposition in the assembly not only from delegates wary of creating legal armor for a future dictator but from leaders across the hinterland seeking to wrest more powers from Moscow. Complicating the picture, the regions want equal status with the 21 republics, while the republics, which have parliamentary representation far out of proportion to their populations, are resisting.

Even if deals can be struck, Yeltsin faces the problem of getting the result adopted as law. Because the assembly has no legal standing, he tried to enhance its legitimacy, and neutralize parliamentary opposition, by inviting members of Parliament this week to join in its work.

Hopes for a breakthrough rose when Viktor Stepanov, legislative Speaker of the republic of Karelia, announced that Yeltsin and Khasbulatov were ready “to meet each other halfway.”

Khasbulatov, 50, a mercurial former professor whose personal feud with Yeltsin has defined Russian politics for the past year, at first refused to take part unless Congress were given the final say over any draft. Then he agreed to attend Thursday’s session to set forth his condition.

Finally, hours before it began, he instructed his spokesman to say he had gone home ill, suffering from high blood pressure. Other reports said Khasbulatov was trying to organize a rival assembly in July.

Fearing that delay can only hurt him, Yeltsin offered to compromise with his critics in Parliament.

He said the assembly was taking a constitutional draft favored by the Parliament and was considering it side by side. Parliament’s draft would give lawmakers greater restraint on presidential power.

In any case, the uncertain outcome of the assembly appears to have dimmed the luster of Yeltsin’s vote of confidence in an April 25 referendum. Foes of the president say he is simply trying to put the best face on a process that has escaped his control.

Sergei L. Loiko of The Times’ Moscow staff contributed to this report.