The Vatican experts were due to arrive in the country last Friday to speak to people who knew Francois-Xavier Van Thuan.

But "the delegation can't come because the government of Vietnam withdrew the visas a few days ago," an official from the archbishop's office of Hanoi told AFP on the condition of anonymity.

Eglises d'Asie (Churches of Asia), the information agency of the Paris Foreign Missions Society, said it had learned from sources that the beatification plans had "angered" Hanoi, whose ties with the Vatican have long been strained.

Thuan was appointed Saigon's assistant archbishop a week before the South Vietnamese capital fell to communist forces in April 1975, marking the end of the Vietnam War.

Thuan, who was the nephew of Ngo Dinh Diem, South Vietnam's first president until his assassination in 1963, was then locked up in a detention camp in the town of Nha Trang.

In his cell, he wrote meditations on his spiritual experiences on the back of old calendars.

After he was freed in 1989, he was forced into exile in Rome, where he eventually was made cardinal by Pope John Paul II. Thuan died in 2002.

Beatification is a high Catholic honour that bestows the title of "Blessed". It is one step away from canonisation, which bestows sainthood.

The Holy See and Vietnam, which have cut diplomatic relations in 1975, have sought to boost relations in recent years.

Vietnamese Prime Minister Nguyen Tan Dung travelled to the Vatican in 2007, while an envoy from the Vatican paid a historic visit to Hanoi last year.

Catholic land confiscated since the end of French colonial rule in 1954 remains a contentious issue between the church and state, and has led to demonstrations.

Vietnam has Southeast Asia's largest Roman Catholic community after the Philippines -- about six million among a total population of 86 million.

Religious activity remains under state control.

Agence France Presse - March 28, 2012