WASHINGTON (AFP) - United States (US) civil rights leader Jesse Jackson said on Monday he was ready to meet North Korea's leader to free an imprisoned American and reduce ill-will between the two countries.

US officials have said that Jackson volunteered to travel to Pyongyang after the totalitarian state abruptly canceled the visit of a US envoy, Robert King, who aimed to free Korean-American tour operator Kenneth Bae.

Jackson said in a televised interview with CNN that he had put "high hopes" in King, but after the trip was called off, wrote a letter to North Korean leader Kim Jong Un.

Mr Jackson said he told Mr Kim he would "like to meet with him face-to-face to seek to work out some mutual respect, some recognising each other's sovereignty, each other's will to peace".

North Korea, which technically remains at war with US-ally South Korea, has defiantly pursued nuclear weapons in what it says is its effort to counter hostility from the US.

Mr Bae, described by a North Korean court as a militant Christian evangelist, was arrested in November 2012 and later sentenced to 15 years of hard labor on charges of seeking to topple the government.

Terri Chung, the prisoner's sister, told CNN that the family was pleading for "mercy". She said that Bae had apologised and was suffering health problems.

Mr Jackson, a longtime activist who campaigned with the late civil-rights leader Martin Luther King, has frequently sought to assist in international crises. He secured Iraqi leader Saddam Hussein's release of US and British citizens before the 1991 Gulf War and later met Yugoslav president Slobodan Milosevic to bring home three US prisoners of war.