Conrad K. Harper said yesterday he “could no longer support” University President Lawrence H. Summers and abruptly resigned from the Harvard Corporation.

The move exposed a rare flash of dissent from University’s seven-member governing body, which appeared to stand by Summers this spring amid harsh criticism from professors.

Harper, speaking from his home in Manhattan, would not elaborate on the reasons for his departure. But individuals familiar with the Corporation said Harper had long been critical of Summers’ management style and opposed his selection as president.

They described Summers’ tumultuous spring semester at Harvard as the final straw for Harper, who was elected to the Corporation in February 2000 and served on the search committee that picked Summers the following year.

“Harper thought Summers should have given up after the no-confidence vote” by the Faculty of Arts and Sciences in March, said a former University official who spoke on the condition of anonymity.

Two people familiar with the Corporation said the relationship between Harper and Summers was irreparably damaged after the president’s public spat with former University Professor Cornel R. West ’74, whom Harper felt had been unfairly rebuked by Summers. The two men communicated only through an intermediary for some time after the incident, the sources said.

Harper declined to comment on his relationship with Summers yesterday, saying only, “I concluded I could no longer support President Summers.” Harper said he had outlined his reasons for leaving the Corporation in a letter to Summers on July 14, but he would not divulge the details of that letter yesterday.

John Longbrake, Summers’ spokesman, said the president would not release the letter. “We regard all Corporation communication as confidential,” Longbrake added.

Harper, the only African-American ever to serve on the Corporation, had been the second-most senior member of the board. With his departure, only James R. Houghton ’58 predates Summers, who is himself a member of the Corporation.

In a statement released by the University, Houghton praised Harper for his “perspective and expertise” but said he was disappointed by Harper’s decision.

“I regret that he has chosen, in reflecting on recent matters at the University, to bring his service to a close,” Houghton said.

Harper’s resignation marks the departure of the only known dissenter on the Corporation. In a four-year period of unprecedented turnover, the board has grown ever more friendly to Summers with additions such as Robert E. Rubin ’60, Summers’ close friend and predecessor as secretary of the Treasury.

One individual familiar with the Corporation said Harper had an increasingly testy relationship with his fellow members on the board. The tension peaked this past semester, according to the source, when Harper refused to put his name on a Corporation statement supporting Summers, who ignited a firestorm on campus with his January remarks on women in science.

Ultimately, the two statements by the Corporation backing Summers bore only Houghton’s name, rather than revealing the 6-1 split on the board.

Many professors who criticized Summers at three contentious Faculty meetings this spring also reserved harsh words for the Corporation, which they described as out-of-touch with the campus.