* Some in traditional Catholic stronghold feel betrayed, angry
* Church figures, Vatican officials urging "faith over politics"
* Vatican has discreet semi-official presence in Hong Kong
* Hong Kong brethren key supporters of China "underground"
HONG KONG, April 1 (Reuters) - A looming deal between the Vatican and China is causing divisions between the church hierarchy and Catholics in Hong Kong, which has long been a vital beachhead for the faith on the southern edge of officially atheist China.
Some senior Catholic clergy and Vatican officials have been urging groups of restive Hong Kong brethren in recent weeks to back a deal many fear will betray the so-called "underground" mainland Catholics that they have been supporting for years.
But some in Hong Kong fear any deal on the appointment of bishops in China could be a trap leading to greater persecution of underground believers as they come into the open, and ultimately to tighter Communist Party control of their religion.
Others, including some whose families fled the communist takeover of China in 1949, are angry the Vatican is prepared to do a deal even when some elderly bishops are in detention and concerns are growing over the party's reach into Hong Kong.
"Some just cannot believe the Vatican would do this, and it is shaking the foundations of their faith," said one missionary priest with more than 20 years experience in parishes on both sides of the border.
"I fear some will turn away from the Vatican."
The 12 million Catholics in China are split between followers of the state's Catholic Patriotic Association, which operates independently of the Pope, and an underground community that swears loyalty to the Vatican.
Vatican officials say a historic agreement with China's leaders on the appointment of bishops could help avoid further division between the two Catholic groups, even if broader diplomatic issues and human rights concerns remain unresolved.
Despite mainland reports that a pact is imminent, a Vatican source said on Thursday there is no timeline for a signing.
'FOLLOW THE LINE'
The Hong Kong congregation has been told to look at any accord "with fresh eyes", to see beyond the politics to consider the long-term importance of building a stronger mainland flock.
"This isn't about politics, it is about faith," said one person familiar with the official message.
One former Hong Kong bishop, Cardinal Joseph Zen, has campaigned against the deal, saying he fears it is communist manipulation of the church, and has publicly sparred with Vatican officials. Another former bishop, Cardinal Tong Hon, has backed it.
Zen told Reuters on Thursday that while he was still "heartbroken" over what he called the Holy See's "betrayal" of Chinese Catholics, the unity of the church should be a priority.
Those without a strong opinion should "follow the line", Zen said. But if some turn away from the Church's leadership, he would not persuade them to change their mind.
"If they simply give up, it's more prudent (than to fight on). It would do less damage to the Church."
'FALLEN INTO A TRAP'
In one recent meeting, a group of some 30 official and underground clergymen visiting from China joined counterparts in Hong Kong for talks with senior Church officials, according to a Hong Kong cleric with knowledge of the matter.
During the hour-long discussion, the mainland clergy expressed anxiety, but fell silent after an official, looking resigned, asked what they would do if they were the Pope.
The cleric, previously critical of the Vatican, now said unity within the Church was the priority.
"We don't have a deal yet, but the church is already splitting up. The Chinese Communist Party doesn't have to do much and it's already enjoying the results," the Hong Kong cleric said.
"We have fallen into a trap."
Hong Kong has for decades been one of the most important Catholic cities in Asia, home to an extensive network of aid agencies, missions, scholars and media that have supported Catholics in China and elsewhere.
Missionary priests who operate underground on the mainland use the city as a base, while other Hong Kong Catholics provide funds and expertise to mainland counterparts.
Catholics are also prominent across Hong Kong's government and business elites, as well as its democracy groups.
Hong Kong's leader, Chief Executive Carrie Lam, is a Catholic who is close to the Beijing leadership. She has not yet responded to Reuters' questions about her thoughts on the deal.
Hong Kong is home to the only Vatican representatives in greater China under Communist Party control, with monsignors operating discreetly out of an art deco villa in the Kowloon suburbs.
The Holy See Study Mission has no formal diplomatic status, given the Vatican's on-going recognition of Taiwan. But it quietly liaises with both Hong Kong and mainland clergy and missionaries.
Western diplomats familiar with their work say the exceptionally low-key mission is monitored closely by Chinese security officials. The Study Mission has not responded to requests for comment.
An Easter editorial in this weekend's Sunday Examiner Catholic paper stressed that "faith needs courage".
"We Christians in Hong Kong are anxious of the prospects of surrendering to the pressures of the atheist government," it said. (Reporting by Greg Torode and Venus Wu; Editing by Tom Hogue)