JERUSALEM — The leader of a United Nations panel that investigated Israel’s invasion of Gaza two years ago has retracted the central and most explosive assertion of its report — that Israel intentionally killed Palestinian civilians there.

Richard Goldstone, an esteemed South African jurist who led the panel of experts that spent months examining the Gaza war, wrote in an opinion article in The Washington Post that Israeli investigations into the conflict “indicate that civilians were not intentionally targeted as a matter of policy.”

“If I had known then what I know now,” he wrote, “the Goldstone Report would have been a different document.”

His article, which was posted on The Post’s Web site on Friday night, follows a report submitted two weeks ago by a committee of independent experts led by Mary McGowan Davis, a former New York judge, that said that Hamas had not conducted any internal investigations of its own but that Israel had devoted considerable resources in looking into more than 400 accusations of misconduct.