VATICAN CITY — The Vatican's top envoy for China says the time has come for the Holy See to get tough with Beijing and not compromise over religious freedom, saying relations are taking a "worrisome slide" for the worse.

Hong Kong Cardinal Joseph Zen also said the Vatican shouldn't give so much importance to re-establishing diplomatic relations with Beijing because such a move could trick people into thinking there is religious freedom in China when there isn't.

And in an interview Tuesday with the Vatican-affiliated missionary news agency AsiaNews, Zen repeated his call for official bishops in China to "not give in" to pressure from the state-sanctioned church, saying they have to remain firm in their faith and loyalty to the pope – even to the point of martyrdom.

China forced its Roman Catholics to cut ties with the Vatican in 1951, shortly after the officially atheist Communist Party took power. Worship is allowed only in state-backed churches, which recognize the pope as a spiritual leader but appoint their own priests and bishops.

Millions of Chinese, however, belong to unofficial congregations that are loyal to Rome. Underground priests and bishops have been harassed or arrested by Beijing authorities.

Pope Benedict XVI has made improving often-tense relations with Beijing a priority of his papacy and has sought to unify the country's 12 million faithful under his wing. But there has been little tangible evidence of progress in his four-year effort, and the Vatican recently denounced a new wave of arrests of underground priests and bishops, and accused Beijing of mounting obstacles to a dialogue with the Holy See.

The Vatican insists that Benedict alone must appoint bishops; China says such papal authority interferes in its internal affairs. In recent years the two sides have reached a compromise of sorts under which both Beijing and Rome agree on candidates.

In 2007, Benedict sent a special letter to Catholics in China, praising the underground church but also urging the faithful to reconcile with followers of the official church. Zen, an outspoken advocate of freedom of worship and a critic of Beijing, said that letter was supposed to have ushered in a new season of relations with Beijing but hasn't.

"We've come to the point where it's not possible and just to accept compromise as we did before," he said. "In these two years there hasn't be a turn toward clarity. In fact, it seems to me that we're taking a worrisome slide along the slope of compromise."

Most worrisome, he said, was a planned assembly of official Chinese priests and bishops this year, which he said would be an "insult to the Holy Father" because it would "completely ignore" his letter.

At the same time, Zen also criticized the Vatican for not having reinforced the 2007 letter, noting that Chinese authorities have tried to block its distribution among mainland faithful.

The Vatican has said it was ready "at any time" to switch its diplomatic relations from Taiwan to China. But Zen warned against moving too quickly.

"Sometimes too much importance is placed on diplomatic relations, when these alone don't set things straight," AsiaNews quoted Zen as saying. "In fact, sometimes it could be misleading because it can give the false impression that religious freedom exists."