Three high-profile Vietnamese bloggers, including one whose case has been raised by US President Barack Obama, are set to go on trial Monday for "anti-state propaganda", a lawyer told AFP.

Nguyen Van Hai, alias Dieu Cay, who has been in detention since September 2008, will go on trial alongside Phan Thanh Hai and policewoman-turned-dissident Ta Phong Tan, lawyer Ha Huy Son said Friday.

"They will be tried under article 88 of the Criminal Code", which covers conducting propaganda against the one-party communist state and carries a maximum sentence of 20 years in prison, said Son, who will represent Dieu Cay.

The trial has been repeatedly postponed, most recently in August after Tan's mother committed suicide by setting herself on fire in front of a local authority building to protest the detention of her daughter, who was arrested in 2011.

Phan Thanh Hai, who blogs under the name Anhbasg, was arrested in 2010.

Nguyen Van Hai was arrested in 2008 and jailed for 2.5 years that September for tax fraud.

Experts said his closed-door trial was likely punishment for his criticism of the government's handling of tensions with Beijing over the South China Sea.

The trio are all accused of posting political articles on the banned Vietnamese website "Free Journalists Club" as well as writing on their own blogs, denouncing corruption and injustice and criticising Hanoi's foreign policy.

In May, Obama said "we must not forget (journalists) like blogger Dieu Cay, whose 2008 arrest coincided with a mass crackdown on citizen journalism in Vietnam".

Human Rights Watch on Friday urged Vietnam to drop all charges against the three and immediately release them.

"Vietnam needs to hear the message that silencing critics and locking up bloggers is not going to help the country solve its problems," said Brad Adams, Asia director at HRW.

Communist Vietnam bans private media -- all newspapers and television channels are state-run. Charges of spreading anti-state propaganda are routinely used to prosecute dissidents.