Myanmar leader Aung San Suu Kyi's defence of jailing of Reuters journalists has prompted a sharp rebuke from the United States.

Suu Kyi, in her first public comment on the case since the two, Wa Lone, 32, and Kyaw Soe Oo, 28, were convicted last week, referred to the colonial-era law under which they were charged. She said jailing of the two journalists had nothing to do with freedom of expression and that they can appeal against their seven-year sentences,

"They were not jailed because they were journalists, they were jailed because ... the court has decided that they have broken the Official Secrets Act," she said at a conference of the World Economic Forum in Hanoi on Thursday.

US Ambassador to the United Nations Nikki Haley described Suu Kyi's remarks as "unbelievable," in what appeared to be the sharpest direct public rebuke of the Myanmar leader by a US official.

"First, in denial about the abuse the Burmese military placed on the Rohingya, now justifying the imprisonment of the two Reuters reporters who reported on the ethnic cleansing. Unbelievable," Haley wrote on Twitter on Thursday.

Speaking at a later news briefing, US State Department spokeswoman Heather Nauert said Washington disgreed with many of the comments Suu Kyi had made and added that the journalists should be released immediately.

"That verdict calls into question press freedom in Burma (Myanmar)," she said.

"The fact that those journalists were convicted despite testimony by police that they were ordered to frame those journalists, that in our view raises serious concerns about the judicial independence and the fair trial guarantees they are supposed to have in that country," Nauert said.

"We continue to urge the government of Burma to take action immediately to correct this injustice."

Suu Kyi made her comments in response to a question from a forum moderator who asked whether she felt comfortable about the reporters being jailed.

Wa Lone and Kyaw Soe Oo were convicted on official secrets charges on Sept 3 in a landmark case that has raised questions about Myanmar's progress towards democracy.

The two reporters, who had pleaded not guilty, were investigating the killing of 10 villagers from the Rohingya minority by the Myanmar security forces at the time of their arrest. The military later acknowledged the killings and said it punished several soldiers.

The United Nations, human rights and press freedom groups and various governments criticised the convictions. US Vice President Mike Pence and US Secretary of State Mike Pompeo have called for their release.

The United States was a strong backer of Suu Kyi as she emerged in the 1980s as a pro-democracy icon who endured years of house arrest for standing up to military rule and was awarded the Nobel Peace Prize for her struggle.

But Western criticism has mounted of Suu Kyi's failure to speak out against military treatment of the Rohingya and of her attitude to the treatment of the journalists.

Earlier on Thursday, Suu Kyi said that in hindsight, her government could have handled the Rakhine State situation better.