WASHINGTON (AP) — James R. Lilley, a longtime CIA operative and later the U.S. ambassador to China during the time of the Tiananmen Square crackdown, has died. He was 81.

The Washington Post said Lilley, who was born in China to an oilman father and schoolteacher mother, died Thursday in Washington from complications related to prostate cancer.

Lilley had a close relationship with former President George H.W. Bush dating to the early 1970s, when Lilley headed the CIA's operations in Beijing and Bush was the chief of the U.S. mission there. During the 1989 Tiananmen protests, Lilley, a stern critic of the crackdown, often sent his reports about the unfolding events directly to Bush, who was then president.

In a statement Friday, Bush called Lilley "a most knowledgeable and effective ambassador who served with great honor and distinction."

Bush said he'd spoken with Lilley just a few days before his death.

Secretary of State Hillary Rodham Clinton, who is traveling in Asia, said she was saddened to learn of Lilley's death and called him "one of our nation's finest diplomats."

She said Lilley "inspired generations of China hands."

Lilley who earlier served as the ambassador to South Korea, was the ambassador to China from 1989 to 1991, "one of the most difficult periods in our bilateral relations," Clinton said.