US lawmakers called for the release of Liu Xiaobo, the world’s only jailed Nobel laureate, and expressed regret on unchanging human rights issues in China.

During a hearing at the Congressional-Executive Commission on China, lawmakers and Chinese friends of Liu vowed to always remember the dissident and his wife, Liu Xia, who has been kept under house arrest since Liu was detained in 2009.

“We have not forgotten Liu Xiaobo and his wife. We commit to seeking their release from confinement and detention. We will not forget them next year, or the year thereafter – regardless of the circumstances,” said lawmaker Chris Smith, co-chairman of the commission.

Liu Min, the wife of Chinese author Yu Jie, urged President Barack Obama to “keep up pressure” on Beijing during a testimony before the commission.

“I hope the American government, especially President Obama, who is also a Nobel Peace Prize recipient, can personally and directly put out a strong call to the Chinese government and demand that they release Liu Xiaobo and Liu Xia immediately,” she said.

Chinese writers and Nobel laureates have separately wrote an open letter to China’s leader-in-waiting Xi Jinping on Liu’s release, AFP reports.