"(Washington) is deeply disturbed at reports of the re-arrest of Bishop Zeng Jingmu," State Department spokesman Richard Boucher said.
"Though we do not have independent confirmation, we are deeply troubled by the reports, given China's record on religious freedom," he added in a statement. "We call on the Chinese government to release Bishop Zeng imnmediately and to permit him to continue his functions as a priest."
"The persecution of an 81-year-old clergyman who has already spent more than 30 years in prison is unacceptable and violates commitments China has made under international human rights covenants and other instruments," Boucher added in a statement.
Boucher said that "(Washington) remains deeply concerned about the continuing detention of religious leaders and members of unregistered churches for attempting to express and manifest their beliefs."
The U.S.-based Cardinal Kung Foundation announced Sunday that Zeng, of Yujiang in the eastern province of Jiangxi, was arrested by police on Sept. 14 together with Liao Haiqing and another priest referred to as Deng.
The Foundation did not list the reasons for their arrest. Foundation officials however noted that Zeng has been under house arrest for the past two years, having already spent more than 30 years in prison for ministering to the "Church of silence," a "patriotic Catholic" institution that has no official recognition from the Vatican yet has been subject to intense scrutiny and penalty from the Chinese government.
China prohibits people from practising their religious beliefs outside official state-sanctioned churches.
The official Catholic Church has around four million faithful, and does not recognize the authority of the pope but is loyal to Beijing.
The underground church, which is loyal to the Vatican, has about 10 million followers.
The Vatican broke with China in 1958 after the Chinese government appointed two bishops.
