Kang Sok-ju, a key architect of North Korea’s nuclear diplomacy who haggled with United States negotiators, once by quoting from a favorite American book, died on Friday. He was 76.

The cause was esophageal cancer, the North Korean government said in a statement. The statement did not say where he had died.

Mr. Kang had been absent from state functions since last summer.

In what was apparently an attempt to drive home his country’s determination to develop nuclear weapons, no matter what the United States said, Mr. Kang once told American negotiators that he would quote from the novel “Gone With the Wind.” He said slowly in English, “The dogs bark, but the caravan moves on.”

Mr. Kang, the most trusted foreign policy aide of Kim Jong-il, North Korea’s leader from 1994 until his death in 2011 and the father of the current leader, Kim Jong-un, was best known for the “agreement framework,” which he negotiated with the United States in 1994 when he was North Korea’s vice foreign minister.