Convicted Soviet spy Arthur James Walker was sentenced here today to life imprisonment and fined $250,000 for his role in an espionage ring masterminded by his younger brother, John Anthony Walker Jr.

Before the sentence was imposed, Arthur Walker, 51, convicted Aug. 9 of seven counts of espionage, said he wanted to "apologize to all the citizens of our country for what I did. No one could be sorrier for anything they ever did."

The sentencing followed a suggestion by federal officials that Arthur Walker may actually have recruited John Walker to spy for the Soviet Union, instead of the other way around, and the disclosure that Arthur Walker had an extramarital affair with John Walker's then-wife, Barbara.

Present in the courtroom were Arthur Walker's wife of 29 years, Rita Walker, who was the only witness to speak on her husband's behalf, and their son Kurt, one of their three children.

Arthur Walker will be eligible for parole in 10 years, but officials said it was unlikely he would be released that soon.

Defense lawyer Samuel W. Meekins Jr. said Arthur Walker told him the punishment was "as expected." But Meekins said he was "stunned" at the severity of the sentence and believed Arthur Walker had been treated unfairly in comparison with his brother and his nephew, Navy Seaman Michael Lance Walker.

He said Arthur Walker, who lived in Virginia Beach before his arrest in May, planned to appeal his conviction.

Under a plea agreement reached last month with federal prosecutors in Baltimore, John Walker, 48, pleaded guilty to three counts of espionage and conspiracy and is to be sentenced to life in prison. He agreed to the plea bargain in exchange for leniency for his son Michael, 22, who also pleaded guilty and is to receive a 25-year sentence. Like his brother, John Walker will be eligible for parole in 10 years; Michael will be eligible in eight years and four months.

Arthur Walker's "greatest culpability is his silence," U.S. District Judge J. Calvitt Clarke Jr. said before imposing the sentence. As John Walker's older brother, Arthur Walker "should have counseled him at the very least to get out of spying , if he didn't want to tell on him."

He also emphasized that Arthur Walker, a retired Navy lieutenant commander, was "an officer trusted by his government with far greater responsibility than either John Walker or Michael Walker."

Clarke conceded that "it may seem unfair to some people that John Walker, because he was a bigger traitor and had more to tell the government, may have gotten a bigger break."

John Walker, a retired Navy communications specialist and former private detective, admitted he had been spying for the Soviets since 1968. He agreed to give investigators a full account of what secrets had been compromised by the espionage ring and to testify at the trial in January of the fourth man charged in the scheme, Jerry Alfred Whitworth.

The judge said that while Michael Walker "apparently gave a good deal more secrets away than Arthur Walker," he also was younger and more susceptible to being influenced by his father.

In addition, Clarke noted, "Sometimes the government just has to hold its nose" and agree to a plea bargain to obtain "desirable information." Clarke said that Barbara Walker, John Walker's daughter Laura Walker Snyder, and Rita Walker, all of whom knew that John Walker was a spy, were "to be greatly condemned" for keeping silent about it for years.

The Walker investigation was launched last November after Barbara Walker informed on her ex-husband at the urging of Snyder.

Defense lawyers had asked Clarke to take the sentences for John and Michael Walker into account and sentence their client to substantially less than life in prison, the maximum sentence.

Defense lawyer J. Brian Donnelly argued that Michael Walker, stationed aboard the aircraft carrier USS Nimitz, was stealing secret documents "by the pounds," while Arthur Walker passed on only two reports labeled "confidential," the lowest category of classified information.

He said a life sentence would send a message that "if you're going to commit a crime, do it on a large scale so you have some trump cards to play."

Assistant U.S. Attorney Tommy E. Miller urged Clarke to impose the maximum sentence and the fine, which he said was necessary to prevent Arthur Walker from reaping the profits of any deal to write a book about the spy ring.

Robert H. Powell III, a lawyer who represents Arthur Walker on noncriminal matters, said he does not have a book contract. But Powell said his client, whose Navy retirement pay was cut off after his conviction, "worries about providing for his family" and "obviously would be interested in pursuing" a book contract.

Miller said that, far from an "unwitting sap" manipulated by John Walker, Arthur Walker was a "traitor" who "sold . . . secrets for a bit of copper." He said John Walker told agents that, three days before his arrest, he asked his brother to try to obtain a report on U.S. defense readiness, and that Arthur Walker agreed to try.

"Never have I felt more strongly . . . that I truly represented the people of the U.S. in asking that the maximum sentence be imposed," Miller said.

Miller said that Arthur Walker "has not been truthful" with the government and "other witnesses have indicated further involvement on the part" of Arthur Walker than he has admitted. He later declined to elaborate.

Before his arrest, Arthur Walker told the FBI and a federal grand jury in Baltimore that John Walker recruited him to spy for the Soviets in 1980, seven years after he retired from the Navy.

He admitted giving his brother John two confidential documents from VSE Corp., a Chesapeake, Va., defense contractor where he worked as an engineer: a training manual on repairing damage on a Navy ship and a report on equipment failures aboard amphibious vessels.

Arthur Walker said his brother gave him two $6,000 payments, but took back half to pay off their business debts.

A Navy expert who testified at Arthur Walker's four-day, nonjury trial called the first document a "Bible for sabotage." A presentencing report said Arthur Walker's actions "jeopardized the safety of every citizen of the United States."

Arthur Walker's lawyers vehemently denied that their client had recruited John Walker to spy or that he had any involvement in espionage during his 20-year Navy career.

They said John Walker backed up that story in an interview with FBI agents Saturday.

But FBI agent Robert W. Hunter, who supervised the Walker investigation, said after the sentencing that it was "a possibility" that Arthur Walker had recruited John Walker as a spy while they were both in the Navy.

Defense lawyer Donnelly said that suggestion apparently stemmed from two statements Barbara Walker made to the FBI.

Barbara Walker said that when she told Arthur Walker she was worried about her husband's spying, Arthur Walker told her not to worry because "he was involved in something like that himself," Donnelly said. He said she also told agents that John Walker had told her she would be "surprised" to learn who had gotten him started in espionage.

Donnelly said Barbara Walker had misunderstood Arthur Walker, who had meant only that he himself had done some wrong things.

Testifying before the sentencing, Rita Walker said her husband "would never injure the United States. He wouldn't hurt anybody, or his country."

Choking back tears, she described relating information to the FBI to help her husband in the days after John Walker's arrest May 20.

"He felt it was his duty [to cooperate with authorities] . . . and it would be better to help," she said. "I didn't realize that I was helping him convict himself."

Arthur Walker's 35 hours of interviews with the FBI and his grand jury testimony comprised the bulk of the case against him. Federal prosecutors conceded he may not have been charged if he had not confessed.

Rita Walker said that, although she did not know at the time that her husband was involved in espionage, she noticed a change in him around 1981, when he started smoking and drinking more and one night came home looking for a shotgun "to blow his brains out."

During cross-examination, Miller asked Rita Walker what she knew about her husband's affair with Barbara Walker during the late 1960s and early 1970s. She replied that her husband revealed the affair on May 25, five days after his brother's arrest.

Meekins said later the discussion of the affair was "part of a [government] plan to draw as dirty a picture as possible."

Arthur Walker was sentenced to serve three life sentences plus 40 years in prison. But all the sentences are to be served concurrently, making his actual sentence no different from that of John Walker, who was sentenced to two life terms plus 10 years, all concurrent.