At midday yesterday vendors were selling Christmas cards and holy pictures outside Notre Dame Cathedral in Ho Chi Minh City, but the front gates to the 117-year-old twin-towered church were locked. To many Vietnamese, this combination of licence and obstruction constitutes a metaphor for the state of religious freedom in Vietnam.
President Clinton repeated several times during his historic four-day visit to Vietnam, which ended on Sunday, that the communist government should allow more political, economic and religious freedoms.
His parting shot as he left Ho Chi Minh City, formerly Saigon, was to predict: "The trend towards freedom is virtually irreversible" in Vietnam.
However, a backlash against any movement for greater freedoms is more likely, at least in the immediate future, judging by the swift and harsh reaction of hardliners in the Hanoi leadership.
Before Mr Clinton had arrived back in Washington, Vietnam's leading general was warning that "hostile forces are fighting against us actively to sabotage socialism and the leading role of the Communist Party of Vietnam."
In a front-page article in an official newspaper Lieut Gen Le Van Dung, chief-of-staff of the Vietnam People's Army, wrote that the military was determined to crush the threat of "peaceful evolution", i.e. any attempt to undermine its political system, before it got off the ground.
Secret documents leaked from within the Vietnam Communist Party in recent days also make Mr Clinton's remarks on an irreversible trend towards freedom seem over optimistic in the short term.
They show that communist officials are alarmed by the possibility of subversion by the Catholic Church, and by the growing number of ethnic minority people converting to Christianity in Vietnam, and indicate that repressive measures taken locally represent official policy.
In Ho Chi Minh City on Sunday, Mr Clinton paid a brief visit to Roman Catholic Archbishop Pham Minh Man. Vietnam's Catholics constitute 10 per cent of the country's 79 million population.
"The situation of the Roman Catholic Church in Vietnam has improved to some extent, but it still faces some difficulties and limitations," Archbishop Man said last week. He acknowledged that three dioceses, Hung Hoa, Hai Phong and Bui Chu, were still without bishops.
Asked about Pope John Paul's wish to visit Vietnam, he said: "The Vietnamese government has responded that it needs a premise, which is relations between Vietnam and the Vatican."
Despite having the biggest Catholic population in Asia outside the Philippines, Vietnam does not have diplomatic relations with the Vatican.
Catholicism was introduced by French colonialists, and the Catholic Church was once the biggest land-owner in the country. Catholics were given key military and civilian posts in the government of South Vietnam, which fell in 1975.
After the Vietnam War many Catholic leaders were sent to reeducation camps, and seminaries were closed. Restrictions on religious groups have been eased since reforms in the 1980s. But Human Rights Watch in New York says that three priests remain in prison along with about 17 other religious figures.
One of 50 "top secret" internal Communist Party documents released by the Washington-based Freedom House said: "The imperialist enemies and their gangs consider using the exploitation of religion as a very important factor in resisting the revolutionary movement."
The document, produced by the Bureau of Minority and Religious Affairs in Lao Cai Province in December 1998, accuses Rome of trying to show Vietnamese Catholics how religious groups helped topple communist regimes in eastern Europe and of broadcasting information into Vietnam "to separate the people from the party".
It accused the United States of fomenting rebellion through the spread of Protestantism, according to extracts published in the Far Eastern Economic Review.
It claimed the number of Protestants in Lao Cai Province had grown from zero in 1991 to 50,000 in seven years.
A more recent document, drafted in May 1999, calls on officials to "stop cold the contagious spread of religion".
While not specifically denying the authenticity of the documents, Hanoi rejected as "distorted" and "slanderous" the charge by Freedom House that authorities were waging a campaign to arrest and reverse the growth of Christianity.
Buddhism, the predominant religion in Vietnam, faced restrictions under French and South Vietnamese rule, and more recently the independent United Buddhist Church has been restricted by the Communist government.
A 73-year-old dissident monk, Thich Quang Do, who has served long jail terms for his activities, complained a month ago that Hanoi refused to allow him to organise private relief for flood victims.
However, during Mr Clinton's visit the restriction was lifted. The government requires all aid to be channelled through state-affiliated organisations.