Pope Benedict is releasing a long-awaited letter today to China's divided Catholics, including millions who worship under a state-controlled Church that does not recognise his authority.
The Vatican said the Pope's letter would be made public at midday and would be addressed to China's bishops, clergy and faithful.
It is expected to seek Catholic unity and improved relations with the officially atheist state. But Italian media reports say the nearly 30-page letter will also emphasise the importance of religious freedom.
China has had no diplomatic ties with the Vatican since 1951, two years after the Communist takeover.
There are about 10 million Catholics in China, split between an "underground" church loyal to the Holy See and a state-approved church that respects the Pope as a spiritual figurehead but rejects effective papal control.
Tensions have flared over the appointment of bishops. China refuses to allow the Vatican to appoint them, saying this would be interference in its internal affairs.
Vatican Secretary of State Tarcisio Bertone was quoted this week as saying the Pope's letter will describe his "desire for dialogue with this great continent".
He said China represented "the future of humanity but also of the Catholic Church", according to Italy's Ansa news agency.
One sticking point in relations is that the Holy See recognises Beijing's diplomatic rival Taiwan. Beijing has insisted diplomatic ties cannot be resumed unless Rome first severs links with Taiwan, which Beijing considers a renegade province.
The Rome-based AsiaNews service, which specialises in China, warned the Pope's letter might prompt a backlash. It said Chinese officials had invited the country's Catholic bishops to a meeting to discuss a response.
"Sources in China fear that the United Front will oblige the bishops to distance themselves from Benedict XVI's message, then to make public statements eulogising the (Communist) Party's religious policies," AsiaNews reported.
The Communist Party's United Front Work Department is responsible for dealing with religious leaders and winning over non-Communists.