Presidential candidate Republican Senator Sam Brownback, meanwhile, backed up the appeal by demanding the man's freedom.
"Right now the purpose of my life is to save my brother," said Son Jong Hoon. "Now I am also praying to God to save my brother.
"Please, please, please write letters to your senators and members in Congress," he pleaded. "Please, please also write a letter to the United Nations. Also please write to government authorities in North Korea."
North Korea is one of the most repressive regimes in the world and is ranked by the ministry Open Doors as the world's worst persecutor of Christians. Citizens of the communist state are forced to adhere to a personality cult revolved around the worship of current dictator Kim Jong Il and his deceased father, Kim Il Sung.
Son was joined Thursday by Senator Brownback who last week sent letters signed by Democratic Senators Max Baucus and Dick Durbin, and Republican Senators James Inhofe and David Vitter to US Secretary of State Condoleezza Rice and UN Secretary General Ban Ki-moon asking them to work to secure the release of the Christian prisoner.
"This is a horrific case. The execution should not occur. It is wrong," said Brownback. "I think the North Korean government, as part of the six-party talks and as a statement of good faith, should not execute this individual.
"I think this is also an indicator of the brutality of the North Korean government. This isn't the first time this has happened."
There were about 300,000 Christians in 1953 but the number has spiralled down to a few thousand who secretly practice their faith, according to VOM.
"The key thing that people need to know about North Korea is that 10 per cent of the population has died over the past 15 years," said Brownback. "You have a massive genocide that has happened because of the North Korean government.
"The weapon of mass destruction has already been deployed [and that] is the government of North Korea because of the gulag system and mass starvation by and at the hand of the government.
"People need to know that," said the senator, who has long been an advocate of human rights and religious freedom in oppressive countries.
