Enten Eller, the clean-cut college senior who claimed God's will left him no choice, today became the first American in the 1980s convicted of failing to register for the military draft.

He was immediately sentenced to three years' probation by U.S. District Court Judge James C. Turk, who ordered the polite 20-year-old, as a condition of his sentence, to comply with the draft registration law within 90 days, or face imprisonment and a fine.

Eller said later he would continue to refuse to register.

"God has led me to this position. I need to be here," Eller told Turk during the 3 1/2-hour, nonjury trial here in which he forbade his attorneys to defend him.

The Justice Department had sought the conviction of Eller, one of about a half-million Americans who have failed to register since President Carter restored draft registration in 1980, as a test case. Four other young men across the country also have been indicted for failing to register, but Eller, an honors physics and math major at church-affiliated Bridgewater College near Harrisonburg, was the first to be tried.

Eller, who had faced up to five years' imprisonment and a $10,000 fine, was sentenced by Turk today as a youth offender, meaning his sentence could be vacated if he should decide to comply with its terms.

During the trial, Assistant U.S. Attorney E. Montgomery Tucker contended that the case was not about religious or moral views or whether there should be a draft, but about Eller's "knowing, persistent, willful and continuing refusal to do an act in accordance with a law of this country."

Under questioning, Eller conceded he had written voluntarily to Selective Service officials and later to U.S. prosecutors here acknowledging that he had not registered.

"Why can't he sign the registration form and say it's not in any way a sign of his approval?" Turk inquired at one point of Rev. Vernard Eller, the youth's father, who is a religion professor and ordained minister in the Church of the Brethren in Le Verne, Calif.

"I've told him that. You try to tell him that," responded the father, who said he had been a conscientious objector during World War II but only after first taking the draft registration step.

Enten Eller testified he had been moved not to comply in part by what he saw as "the inequity" of receiving automatic conscientious objector status as a member of the Church of the Brethren, one of several historic pacifist denominations in the United States.

The Brethren, which date from 1723 in this country, now number about 170,000 members and are headquartered in Elgin, Ill., according to church officials.

On two occasions, about 100 of Eller's supporters, who crowded Turk's second-floor courtroom, interrupted the proceedings with applause. One outburst followed Eller's father's observation that, "if nobody would sign draft registration cards , we'd have a real peaceful world."

A second round of clapping, which drew a stern look from the judge, came for church official Charles Boyer's acknowledgment while on the witness stand that he and his wife are tax resisters who refuse to support the U.S. military budget.

Turk appeared more sympathetic to the youthful-looking Eller, who was dressed in a navy blue vest, white shirt and tie, and whose brown hair fell to the bridge of his metal frame glasses. Turk gently questioned him about his religious views.

"You could claim you were the target of selective prosecution" by the Justice Department, the judge observed.

"I might believe it, but I don't wish to contend that," replied Eller.

"You're telling the court you can't do otherwise" than refuse to register? asked Turk a moment later.

"That's right," said Eller.

"I'm not trying to get myself in hot water," he continued. "I'm not trying to be a martyr. I didn't want a lot of publicity. I turned down appearances on the Phil Donahue Show and Sunday Morning."

"Do I understand that your life is a struggle for closeness to God?" Turk asked.

"That's it," said Eller. "In God We Trust. I'm trying to live up to that motto."

Two local lawyers, Arthur Strickland and Jonathan Rogers, assisted Eller in the case, but told Turk they had been frustrated by Eller's decision not to mount a legal defense. Both attorneys said they believe the draft registration statute is unconstitutional.

Today's trial was preceded by a 30-minute prayer vigil under the American flag flying outside Roanoke's modern federal courthouse. Eller supporters stood in a circle as one Church of the Brethren official declared, "We love our country, but we believe the direction of destroying other people is not the direction for us . . . We hope people of this community, state and the world will feel their consciences pricked by this act of conscience by Enten Eller."