President Barack Obama said Tuesday he was concerned about an American citizen who was sentenced to seven years of hard labor by the Myanmar junta.

I am concerned by the sentencing of American citizen John Yettaw to seven years in prison, a punishment out of proportion with his actions, Obama said in a statement.

John Yettaw, 54, a Mormon swam across a lake to Aung San Suu Kyi's lake side home in May and stayed there for two days. That breached Suu Kyi's house arrest and a security law protecting the State from subversive elements.

Yettaw told the court God had sent him to warn Suu Kyi she would be assassinated by terrorists.

He was sentenced to seven years' hard labor in a parallel trial on three charges, including immigration offences and swimming in a non-swimming area.

His lawyer said the American suffered from epilepsy, diabetes and heart trouble and was taken to hospital last week after suffering seizures.

Myanmar's opposition leader Aung San Suu Kyi was also sentenced Tuesday to 18 months in detention, a verdict that drew condemnation abroad and will keep her off the political stage ahead of next year's elections.