The Justice Department will not recommend a light sentence for convicted spy Arthur Walker in exchange for his testimony against his brother, accused spy John Anthony Walker Jr., or the other two Navy men charged in the alleged espionage ring, the head of the department's criminal division said yesterday.

"We're not horse-trading," Assistant Attorney General Stephen Trott said in an interview. If Arthur Walker agrees to testify against his brother, he said, "We will tell people, 'We're delighted that you're interested in truthful cooperation with the government. But you're doing that on your own motion, not because we're promising to give you anything in return.' "

Arthur Walker's lawyers said after his conviction Aug. 9 on seven counts of espionage that he was willing to testify against John Walker, whom authorities have described as the mastermind of the alleged spy ring. Sentencing for Arthur Walker, who faces a possible three life terms plus 40 years in prison and a $40,000 fine, is set for Oct. 15. John Walker's trial is scheduled to begin Oct. 28.

Prosecutors often agree to recommend a lighter sentence, or to withhold recommendations on sentencing, in exchange for the testimony of a convicted criminal against others charged in the case.

In return for Arthur Walker's testimony at his brother's trial, Arthur Walker's lawyer, Samuel J. Meekins Jr., said yesterday, he would "expect the government to give up their right to argue at the sentencing hearing" and to "get them to acknowledge that he's cooperating and to transmit that to the court."

But Trott said that he thought it was "a rotten idea" for the government to give up its right to speak at the sentencing hearing. Although "we will gladly advise the sentencing judge of what, if anything, Arthur Walker does" in terms of cooperation, "we will say what we want to say" about his crime, Trott said.

"We're not giving anything away in this case," he said. "We are making no promises."

The hard line on a sentencing recommendation for Arthur Walker continues the department's tough stance in espionage cases. Arthur Walker's lawyers told prosecutors their client was willing to plead guilty to conspiracy to commit espionage, the most serious charge against him, and on the morning the trial began, offered as well to plead no contest to the other six counts.

But Justice Department officials refused to accept anything but a guilty plea to all seven counts, an attitude that may indicate its stance on a possible plea bargaining arrangement with John Walker and the two others charged in the case, John Walker's son, Navy Seaman Michael Lance Walker, and retired Navy communications expert Jerry Alfred Whitworth.

"I think we set the standard in Arthur Walker's case for handling all espionage cases that you're going to see in the future," Trott said. "Our general policy in espionage cases is to regard them as extraordinarily serious and not to make any concessions at all unless its absolutely necessary."