HANOI (AFP) -- Vietnam's ruling Communist Party is readying for its crucial five-yearly party congress starting Tuesday amid a sordid corruption scandal that has already claimed several government scalps.

Fighting graft will be key to defending the party's legitimacy, top party officials have conceded, as public anger has grown over revelations that corrupt transport ministry cadres embezzled millions of dollars. "The congress is going to be overshadowed by the issue of corruption," said Martin Gainsborough, a Vietnam expert at Britain's Bristol University, speaking ahead of the April 18-25 event. "We have a situation that demands a clear and convincing response from the top."

The talk on the street may be about graft and impunity, but the Soviet-style congress will follow long-established rules that stress stability and continuity in one of the world's five remaining communist countries.

Red banners over Hanoi's streets welcome nearly 1,200 party delegates to the event that will set the political and economic course of the nation of 83 million people until 2010.

Delegates representing 3.1 million party members will recommit to Marxism-Leninism, Ho Chi Minh Thought and 20-year-old Doi Moi (renewal) reforms toward a "market economy with socialist orientation".

Backroom brawls may have raged between reformers and hardliners, and between factions that advocate closer ties with China or the United States.

But outwardly the party that stresses consensus is unlikely to announce radical shifts in direction.

"There will be no major change in policy," said Phan Dien, permanent secretary of the party's central committee.

He said, however, that "the upcoming central committee and politburo will be subject to a lot of changes" when party members choose the new 160-member committee and the elite politburo with at least 15 members.

Prime Minister Phan Van Khai and President Tran Duc Luong may leave the politburo, meaning they would retire from their government posts in 2007, analysts say, and there is speculation on whether General Secretary Nong Duc Manh will stay in Vietnam's most powerful post.

But even seasoned Vietnam watchers have shied away from predicting personnel changes amid the country's worst post-war corruption scandal.

Early this month Transport Minister Dao Dinh Binh resigned and his deputy was jailed over revelations officials in the ministry's Project Management Unit 18 (PMU18) fleeced funds earmarked for highways and other infrastructure.

The scandal broke in January with the arrest of PMU18 head Bui Tien Dung for betting seven million dollars, much of it from Japan and the World Bank, on European football matches.

The affair has since become a can of worms that has implicated figures in the top echelons of the party.

The state-controlled press has been allowed to report aggressively that officials took kickbacks, bought luxury homes and sought to pay off police and officials for protection.

A newspaper reported Friday that police had cleared top officials including cabinet minister Doan Manh Giao, head of the government office, of being involved in the scam.

At the weekend, the state press said police were investigating whether a Vietnamese opera actress led a prostitution network that offered girls to corrupt PMU18 officials.

Some ageing revolutionaries see a betrayal of what they fought for.

"There is now a serious crisis of trust among our people and in our party," ex-interior minister General Mai Chi Tho was quoted as telling the Tien Phong newspaper.

National hero General Vo Nguyen Giap, who led Vietnamese forces to victory against French and US troops, thundered in the Tuoi Tre daily that "the party has become a shield for corrupt officials".

The party is aware of the problem. Politburo member Phan Dien last week described corruption as a threat to "the survival of our political system".