The National Endowment for the Arts appeared to clear a major hurdle yesterday when the Senate approved a $170 million appropriation for the agency and defeated an effort to restrict public funding of sexually explicit art. But at the last minute, Sen. Jesse Helms (R-N.C.) apparently caught some senators off guard and won voice vote approval of an amendment forbidding funding of material that denigrates religion.

The impact of the Helms measure was not immediately clear, but Senate sources predicted it would not survive a conference to reconcile the House and Senate versions of the legislation.

Before the Helms amendment, the Senate voted 73-24 for a compromise approach that includes no content restrictions but empowers the NEA to recoup funds from grant recipients whose work is found in court to be obscene or to violate child pornography laws. The House has approved similar legislation.

If the Helms amendment is eliminated, controversial content restrictions imposed in the fiscal 1990 appropriation could be a thing of the past. Those restrictions forbid funding of works that "may be considered obscene, including, but not limited to, depictions of sadomasochism, homoeroticism, the sexual exploitation of children, or individuals engaged in sex acts and which, when taken as a whole, do not have serious literary, artistic, political, or scientific value." Several artists and arts organizations had rejected endowment funding to protest that legislation and an NEA requirement that they pledge compliance with the restrictions.

The funding bill will extend the endowment for a year. A measure to reauthorize the federal agency is not expected to reach the Senate floor before Congress adjourns.

Early in the debate, Helms, the endowment's leading opponent in the Senate, appeared to be acknowledging defeat on the content restriction issue. But he vowed to continue the battle next year if he wins reelection.

"I say to all of the arts community and homosexuals who may be upset... . What is past is prologue. You ain't seen nothing yet," Helms said.

But after the Senate had rebuffed efforts to impose content restrictions and had approved the compromise, Helms proposed and won approval of the amendment blocking the endowment from funding "material which denigrates the objects or beliefs of the adherents of a particular religion." The measure passed on a voice vote in the nearly empty chamber. Sen. Claiborne Pell (D-R.I.), one of the leading sponsors of the compromise legislation, had issued a press release stating that the funding bill had passed "without content restrictions." Pell acknowledged later that he was surprised by the Helms measure but said it "was not of huge significance."

By the time the Helms measure was introduced, Sen. Orrin Hatch (R-Utah) -- a leading sponsor of the compromise -- had left the chamber and proclaimed victory. But he warned that the NEA should avoid offensive work.

After the compromise amendment passed, Hatch said he had to leave the floor and expected the Democrats to shepherd the legislation to final passage. "I think people thought that once they won on my amendment, that was all that needed to be done," he said. If Pell had called for a formal vote, Hatch said, the Helms amendment might still have passed, making it that much more difficult to remove in conference.

According to the compromise legislation approved by the Senate, the NEA may recoup funds from grant recipients convicted on obscenity or child pornography charges and may bar those recipients from receiving new grants for three years. The House bill does not impose the latter penalty if funds are repaid promptly. The House would allot $180 million for the agency.

The House version contains no language on child pornography. But it includes language urging the NEA chairman to ensure that grants will be awarded "taking into consideration general standards of decency and respect for the diverse beliefs and values of the American public."

In addition, the House version increases the percentage of grant money allotted to state agencies from 20 percent to 27.5 percent.

The Senate defeated by 70-29 a Helms proposal to forbid funding of "materials that depict or describe, in a patently offensive way, sexual or excretory activities or organs." Helms also attempted unsuccessfully to deny grants to artists who earn more than a certain income level.

There was no debate on the Helms religion restriction, but Pell and Hatch had argued earlier that content restrictions are unconstitutional. Hatch said the sanctions in the compromise proposal are a constitutional approach to enforcing anti-obscenity provisions.

"Congress has never been successful in setting {explicit} standards when the matter at hand is so subjective in nature," Hatch said.

Hatch spoke emotionally about his childhood violin lessons and the importance of art in his life. "To my dying day, I'll be grateful for what the National Endowment for the Arts ... has done for my home state," he said.

But Helms was not persuaded. "If there has ever been more irrelevant oratory than we have just heard ... I have never heard it," he said. "I played the violin too when I was a little boy. ... We're not talking about violins. We're talking about the kind of art where a photographer is subsidized and rewarded because he took a picture of a naked man with a riding crop protruding from his rear end."

Helms argued that the sanction provisions will be ineffective, citing the recent acquittal of the Contemporary Arts Center in Cincinnati. The gallery had been indicted for displaying homosexual and sadomasochistic images by photographer Robert Mapplethorpe.

Artists "are not going to be taken to court," Helms argued. "You saw what happened in Cincinnati. We can't duck our responsibility here. But the Senate is ducking it."