U.S. District Judge Albert V. Bryan Jr. yesterday cut in half the bond for convicted spy Ronald L. Humphrey, saying that it was unfair for the former U.S. Information Agency officer to remain jailed while his codefendant, David Truong, was free on bond. Both men are appealing their convictions on charges of spying for Communist Vietnam.

"The chance of flight of Mr. Humphrey is less than the chance of flight of Mr. Truong," the judge said. "Mr. Truong's out on bond. It doesn't seem fair."

Bryan then ordered that Humphrey can be freed from the Alexandria city jail if he can post a $75,000 bond, half the amount of the bond another judge had previously set. Humphrey, who has been jailed since his arrest Jan. 31, should be able to post the bond, his lawyer, Mark Foster, said later.

Humphrey and Truong were convicted in May of funneling classified diplomatic cables to the Vietnamese in Paris and sentenced to 15 years in prison.

Bryan had revoked Truong'd $250,000 bond after the convictions, but Truong was freed on bond last month after Supreme Court Justice William J. Brennan Jr. ordered hisbai 1 reinstated.

District Judge Oren R. Lewis then ordered Humphrey's previous bond reinstated in light of Brennan's decision:

During a brief argument yesterday before Bryan Foster said that Truong "is lucky enough to have wealthy relatives and friends and political connection's" to raise his bail. Truong, once a Capitol Hill lobbyist for Vietnamese causes, made his bond through donations from church groups, friends, and a sister in Los Angeles.

Foster asked that Humphrey be released on his personal recognizance. "If your honor is willing to do that I'll stop talking," Foster said. "You can keep talking," Bryan said smiling.

Some of the church groups that helped Truong did so partly because he is a member of a minority and partly because he revived anti-Vietnam war sympathies. Foster said that a lower bond "would create a network of people around the country" whowould assist Humphrey.

U.S. Attorney William B. Cummings opposed a reduction in Humphrey's bond and said that such a request should have been made before the trial.