Steven Rhodes, a senior adviser to President Bush when he was vice president, has resigned after less than five months as U.S. ambassador to Zimbabwe because of what the State Department describes as "personal reasons."

Rhodes, 39, was recalled to Washington in August after the State Department received an accusation from Zimbabwe that he had been involved in an incident involving drugs there earlier in the summer, a senior administration official said yesterday.

The official said Rhodes was not under criminal investigation in either nation. The official said Rhodes resigned after "discussions" with State Department authorities here over a two-month period. A spokesman for the department, Adam Shub, said Rhodes submitted his resignation to Bush Oct. 4.

"As in any case in which a resignation is submitted by an individual for personal reasons, it is the department's practice not to comment on the reasons involved," Shub said.

Shub said Rhodes has what amounts to a 90-day grace period before he leaves government. Reached at a hotel here, Rhodes declined comment.

The first notice of Rhodes's resignation appeared last week in Harare's daily newspaper, according to Knight-Ridder News Service, which reported the resignation Monday. The resignation was announced in Zimbabwe by the U.S. Information Service, which attributed it to personal and health reasons. The resignation was not announced here.

The account in the Harare Financial Gazette alleged that Rhodes was pushed out of his post by "immense political pressure" because he had not pushed the government aggressively enough on human rights abuses and multiparty democracy.

The story suggested Rhodes was in dispute with the State Department about U.S. policy toward Zimbabwe, but department officials denied that yesterday. "Policy, I am sorry to say, had nothing to do with it," one administration official said.

Officials would not provide further details of the alleged drug incident. "There was an incident involving drugs," an official noted. "Discussions were held. He is now gone. That is all we have to say about it."

Rhodes's route to an ambassadorship originally went through the Ronald Reagan White House, where he served as a special assistant in intergovernmental affairs when the former president took office. He had gotten his post through Justin Dart, a close friend of Reagan, who employed Rhodes in Los Angeles for eight years before Reagan's inauguration.

Rhodes began working for Bush as his senior domestic policy adviser in 1983, advising the vice president on domestic issues and politics and serving as a liaison with the black community. He was part of the small inner circle of Bush aides in the vice presidential years and retains ties to many senior aides who serve the Bush administration.

In 1985, Rhodes left to join a New York investment banking firm, and in 1987 he returned to Los Angeles, where he operated a Smith Barney financial office and was involved in California GOP operations. Bush nominated him last November to become the first black ambassador to Zimbabwe.

The Senate confirmed Rhodes in March, and officials of the Senate Foreign Relations Committee said yesterday that nothng arose in his confirmation hearings to disqualify him for the post.

Like many Bush ambassadorial nominations from the political, rather than career foreign-service world, Rhodes was questioned by senators and professional foreign-service groups about his qualifications.

He had no foreign-policy experience, and in his only public statement on Africa, had called on American blacks to end preoccupation with sanctions against South African to combat apartheid and pay more attention to U.S. budget and tax policies that he said affected them more.