HONG KONG/SHANGHAI (Reuters) - Chinese authorities have detained an “underground” bishop who is being asked to take a subordinate role in the church as part of a landmark deal between the Vatican and China’s Communist government, two sources said on Wednesday.

The sources with knowledge of the matter said Guo Xijin, known as an “underground” bishop as he has not joined the Chinese state-controlled Catholic Patriotic Association that operates independently of the Vatican, had been picked up by security officials in Fujian province.

The Catholic news outlet Asia News reported on Tuesday that Guo had been detained after he declined to officiate Easter masses with Zhan Silu, one of seven Chinese government-appointed bishops not recognised by the Vatican.

Asked about the case, a spokesman for the U.S. State Department said that no one should be detained or harassed for peacefully expressing their views.

“We urge the Chinese government to cease policies that unduly restrict the exercise of freedom of religion or that otherwise deny individuals their ability to enjoy their human rights‎,” he said.

Catholics in China are split between “underground” communities that recognise the pope and those belonging to the Catholic Patriotic Association where bishops are appointed by the government in collaboration with Church communities.

One of the sources familiar with the matter said Guo and two priests in Fujian were detained. A second source, with extensive contacts in the underground church, said Guo had been taken away for a day but had since returned to his diocese.

Both of the sources declined to be identified because of the sensitivity of the matter. Neither said why Guo had been detained.

The Ningde City public security bureau in Fujian and the Fujian Provincial Bureau of Nationalities and Religious Affairs did not answer repeated telephone calls.

China’s Ministry of Public Security did not immediately respond to a request for comment. Foreign Ministry spokesman Lu Kang said he had no understanding of the situation, but the government fully protected people’s right to freedom of religion.

Guo’s detention comes as unprecedented efforts are underway between Beijing and the Vatican to resolve the thorny issue of who gets to appoint bishops.

‘AUXILIARY’

A senior Vatican source told Reuters last month a framework accord was ready and could be signed in months. It could open the way for a resumption of diplomatic relations nearly 70 years after they were cut during the Communist takeover of China.

Full relations would give the Catholic church a legal framework to look after all of China’s estimated 12 million Catholics and allow it to focus on growth in a country where Protestant churches are already growing fast.

Under the expected deal, the Vatican would have a say in negotiations for the appointment of future bishops, Reuters reported in February.

In order to facilitate it, the Vatican-recognised bishop Guo was being asked to become an auxiliary to the government-appointed Zhan, the Vatican source said.

Critics of the deal - including Cardinal Joseph Zen, the outspoken former bishop of Hong Kong - have suggested the Vatican is about to “sell out” those Catholics in China, like Guo, who have remained loyal to the Vatican and suffered hardship for doing so.

Asia News said in its report Guo had been detained for 20 days last year over Easter.

Any deal between the Vatican and Beijing would likely leave Taiwan in the diplomatic lurch.

The Vatican is one of only 20 states that still recognise self-ruled Taiwan, officially known as the Republic of China. Beijing insists that if countries want relations with it they must break ties with Taiwan.