Mayor Marion Barry said yesterday he felt betrayed by Jesse L. Jackson's failure to support his candidacy for an at-large seat on the D.C. Council, contending he had helped the civil rights leader "more than anybody in this town."

Jackson, who is a candidate for a shadow Senate seat from the District, said last week that he was supporting incumbent Hilda H.M. Mason of the Statehood Party and Democratic nominee Linda W. Cropp for the two at-large seats that will be filled Nov. 6.

"Jesse Jackson's support of another candidate is an indication of a problem he has, and that is of betraying and going against people who helped him over the years," Barry said during an appearance on the Diane Rehm Show on WAMU-FM. "I've been a strong supporter. I've helped Jesse Jackson more than anybody in this town."

Barry added, "You learn in this world that life is not fair and people are not fair." Asked if he felt Jackson had been unfair to him, he said, "If the shoe fits, you wear it."

In an interview with Barbara Walters taped for broadcast tonight on ABC's "20/20" program, Barry complained again about Jackson's failure to support him.

Barry's comments about the campaign represent the second time this year he has publicly criticized Jackson. In an interview with the Los Angeles Times in January, Barry scoffed at the possibility that Jackson would run for mayor, saying, "Jesse don't wanna run nothing but his mouth."

Barry could not be reached for additional comment about his reference to Jackson's "problem" with "betraying" friends.

But he has told acquaintances in recent days that Jackson's decision not to endorse him angered him because he was one of the earliest and strongest supporters of Jackson's 1984 presidential campaign.

Jackson, in several telephone interviews yesterday, said Barry's reference to having been betrayed was "unfortunate, but I remain his friend" and "I think our relationship is operational."

"At his lowest and loneliest moments, I was with him and his family, offering spiritual and material help, and I remain with him," Jackson said in a reference to Barry's arrest and trial on drug-related charges this year. Barry was convicted of cocaine possession and is to be sentenced today.

Jackson, who said he and Barry had not talked about the campaign or about Barry's unhappiness, said he decided to support Mason before Barry announced his candidacy for the council. He said Mason is one of the founders of the Statehood Party, and "I'm running for statehood senator."

"I support the Democratic ticket. I have sought to be the party's standard-bearer on two occasions and unless there are extenuating circumstances, I will support the party," Jackson said. Barry left the Democratic Party earlier this year to run as an independent.

Jackson said he "certainly hoped" that Barry's comments did not mean the mayor would oppose Jackson's candidacy for shadow senator.

In the "20/20" interview, Barry repeated that he and other black officials have been investigated and prosecuted by the federal government because of their race, "and so you have to conclude there's something wrong in this country."

But Barry said he was not using race as an excuse: "I have not made any statements about race, except in the context that I believe that this administration was unfairly sin singled out."

Earlier yesterday on the Diane Rehm program, the Republican and Democratic nominees for D.C. delegate for Congress engaged in an often barbed and personal duel of differences, picking apart each other's careers and values.

Much of the one-hour exchange between Democrat Eleanor Holmes Norton and Republican Harry M. Singleton, both Yale-educated lawyers, focused on how each was involved years ago in defending the free-speech rights of figures anathema to blacks.

While an attorney for the American Civil Liberties Union, Norton defended a white supremacy group that had been denied the right to hold a rally.

And while he was a student at Yale, Singleton had defended the right to speak of William Shockley, a physicist who argued that blacks were genetically inferior.

Singleton called Norton's action "reprehensible." Norton shot back that Singleton had taken a similar stance, and that she regarded her defense of a First Amendment case as one "of my proudest moments."