Two senior Vatican officials have traveled to China to sound out possibilities of re-establishing diplomatic relations, seeking to overcome a major dispute over the Vatican's tradition that the pope names his bishops.

While Pope Benedict XVI has repeatedly expressed hope that the Vatican can achieve an opening with China, the need for religious freedom has become a major theme of his 14-month papacy.

"I think the Vatican holds out no great hopes from the trip," said the Rev. Bernardo Cervellera, head of AsiaNews, a missionary news service that identified the members of the Vatican delegation. "But it is important that the door is open to continue dialogue," he told The Associated Press.

The visit was also reported by a Hong Kong newspaper. China's Foreign Ministry would not confirm it.

Vatican spokesman Joaquin Navarro-Valls issued an unusual one-line statement saying "I have no comment to make" — but he didn't deny the report, which was seen here as confirmation of the mission.

AsiaNews, which is close to the Vatican and the Catholic Church in China, said Monsignor Claudio Celli, a Vatican diplomat, and Monsignor Gianfranco Rota Graziosi of the Secretariat of State have been in Beijing since Sunday and would remain until Saturday.

Ties with the Vatican were broken in 1951 after the communists took power in China. Worship is only allowed in government-controlled churches, but millions belong to unofficial congregations loyal to Rome.

The Vatican already has indicated willingness to resolve one issue with China, switching diplomatic recognition to Beijing from Taiwan. The communist mainland claims Taiwan as part of its territory and refuses to have relations with any nation that recognizes the self-ruled island's popularly elected government.

Vatican Foreign Minister Archbishop Giovanni Lajolo repeated the Vatican's position in May. "It seems to me that the Holy See has clearly explained what it is asking for, what it is ready to concede and what it can never give up if it is to remain faithful to itself," he said.

The major stumbling block is a dispute over who has the power to appoint bishops.

China's state-sanctioned Catholic Church, the Chinese Patriotic Catholic Association, has appointed bishops without the pope's approval. The Vatican recently invoked a rule suggesting that those who took part in the ordination would be excommunicated.

The Vatican rejects most government involvement anywhere in the world in the selection of its hierarchy, but it has made exceptions. In Vietnam, another Asian communist nation, bishops are appointed after consultation with the government.

AsiaNews said the issue is further complicated by the periodic crackdowns against the underground church in China that is loyal to the pope, including the arrests of dozens of priests.

"It has also become clear, from the beginning of Benedict XVI's pontificate, that the Vatican is seeking diplomatic relations as a means to full religious freedom for the church," the agency said.

Benedict's elevation to cardinal in May of Hong Kong Bishop Joseph Zen, an outspoken champion of religious freedom, was an example of the pope's vision for China.

Zen said he was aware of a planned visit by Vatican envoys.

"I don't have any detailed information," he said. "The Vatican hasn't told me anything, I just know people from the Vatican were planning on going to China."