James G. Bellows, editor of The Washington Star, is expected to resign soon after almost three years in the newspaper's top newsroom post, according to reliable sources.

According to Hearst Corp. officials, Bellows is close to an agreement to become editor of the Hearst-owned Los Angeles Herald-Examiner. Bellows declined last night to comment on the reports, saying, "I wouldn't want to discuss that."

At the same time, Star officials notified the newspaper's employees yesterday that there may soon be a sizeable reduction in the Star's staff. Bellows referred to a "coming staff reduction" in a recent memo, according to Star employees. Bellows also announced in the memo that the Star was "going to have to cut out all freelance" articles, which the newspaper has frequently used to supplement the output of its own news staff.

Staff members of the Star, who asked not to be identified, said the newpaper's management warned during a meeting of department heads yesterday morning that the staff reductions may amount to 10 per cent of the newspaper's overall work force. Newsroom sources said the reduction there could mean the loss of 25 news staffers.

The reports of Bellows' expected departure and threatened staff reductions had a demoralizing effect in the Star newsroom. "It's mind-boggling," said one reporter. Describing Bellows as "just absolutely tops," the reporter added, "How could you allow a guy like that to slip through your fingers?"

While the cause of Bellows' anticipated resignation was not altogether clear, reliable Star sources said friction had recently developed between Bellows and Star chairman Joe L. Allbritton. Some sources cited Allbritton's hiring last spring of James H. Smith, former general manager of the Sacramento, Calif. Bee, as Star president, who had been pressing for changes, including staff reductions, to imporve the Star's financial position.

Neither Allbritton nor Smith could be reached for comment last night.

In a telephone interview last night, Los Angeles Herald-Examiner publisher Frank Dale denied that Bellows had yet been hired, but he did not rule out the possibility. "I am talking to Jim Bellows about a lot of things," he said. "One of the things he has been very helpful with is giving me names (for the position), but I can't tell you whether or not there is anything to it at all.

Another source close to the search for a Herald-Examiner editor described Bellows as having been among five contenders for a job that includes total editorial control of the newspaper and a salary of $75,000 to $100,000. Other sources said Bellows had recently resumed serious negotiations with the Herald-Examiner.

Bellows was brought in as the Star's editor in December, 1974, shortly after Allbritton gained control of the newspaper and began efforts to halt the Star's downward financial spiral. Bellows had been editor of The New York Herald Tribune before its collapse in 1966 and was later an associate editor of The Los Angeles Times.

At the Star, Bellows has been credited with a number of editorial changes designed to make the Star livelier than it had been.

The warning of possible staff reductions at the Star came at a time when the newspaper's financial health had seemed to have been improving. Earlier this year, the Star reported an operating profit of $582,000 for the three months ended June 30 - its first quarterly earnings for what it termed "normal operating conditions" since the end of 1970.

The Herald-Examiner, the afternoon competitor of the Los Angeles Times, has faced severe difficulties in recent years. It has been a financial drain on the Hearst Corp. since it was crippled by a bitter and costly strike by its unions 10 years ago. Its circulation has fallen from over 750,000 in 1967 to just over 300,000 today. The strike has now been settled with out-of-court payments to unions and efforts to rejuvenate the newspaper appear to be under way.