SEOUL (Kyodo) The United States and Japan put intense pressure on the military-backed government in South Korea in 1980 to prevent the execution of then leading dissident Kim Dae Jung, Yonhap News Agency reported Monday, citing declassified diplomatic documents.

U.S. lawmakers pressured the government of President Chun Doo Hwan through resolutions, statements and letters to the general-turned-leader, warning of jeopardized relations, cutting of exchanges and the suspension of economic assistance if Kim, who later became South Korea's president, was executed over trumped-up charges of treason, the documents show.

Japan also pressed the South not to carry out the execution, saying it would put a great strain on relations between the two countries and warning that an execution could force Tokyo to seek greater exchanges with North Korea, according to the documents declassified 30 years after their production.

Kim went on to serve as president for five years from 1998 and won the Nobel Peace Prize in 2000. He died in 2009.

"Should the death sentence now facing Kim Dae Jung be carried out, then the traditionally strong relationship between the United States and the Republic of Korea could itself be put in jeopardy," nine U.S. lawmakers, including Rep. Lester Wolff, said in an Oct. 3, 1980, letter to Chun, the documents show, according to Yonhap.

In 1980, Kim and other leading opposition figures were arrested on charges of treason by Gen. Chun Doo Hwan, who imposed martial law as he moved to take over the presidency following the assassination of President Park Chung Hee a year earlier.

Kim Dae Jung was sentenced to death for allegedly fomenting a democracy uprising in the southern city Gwangju.