YANGON - Myanmar's Supreme Court is set to rule Friday on detained pro-democracy leader Aung San Suu Kyi's appeal against an internationally condemned 18-month extension to her house arrest.

The 64-year-old Suu Kyi had her detention lengthened in August after being convicted over a bizarre incident in which an American man swam to her house. A lower court rejected an initial appeal in October.

The court will issue its verdict at 10:00 am (0330 GMT), according to a notice posted outside the court building in Yangon on Thursday evening.

If the Supreme Court rejects her case, Nobel Peace laureate Suu Kyi can make a final appeal to Myanmar's chief justice. She has already spent most of the last 20 years in jail or under house arrest.

Her lawyer Nyan Win said he would not preempt the decision.

"I do not want to guess what the Supreme Court's verdict will be, but she is clearly not guilty," Nyan Win, who is also the spokesman for her National League for Democracy party, told AFP Thursday.

Suu Kyi has previously dismissed comments by Home Affairs Minister Maung Oo, who reportedly said she would be released in November, as "unfair" ahead of any court decision.

The NLD won elections in 1990 by a landslide but the military government never allowed it to take power.

The junta has promised to hold the first elections since then at some point this year, but has refused so far to set a date and critics say they are aimed at simply entrenching the generals' power.

Suu Kyi is effectively barred from standing in the promised polls and a quarter of the parliamentary seats up for grabs are reserved for the military.

She has said it is too early for her party to decide whether to participate in the elections while freedom of expression remains elusive.

At least 2,100 other political prisoners remain behind bars in Myanmar, according to UN figures.

Friday's ruling comes a week after UN human rights envoy Tomas Ojea Quintana visited the country, saying as he departed that he "deeply regretted" being refused access to Suu Kyi during his five-day trip.

Myanmar's government has given out mixed signals ahead of the polls, in mid-February releasing deputy NLD leader Tin Oo after seven years, but days later jailing a US activist for three years.

The regime jailed a further five dissidents during the visit by the UN special rapporteur.

Suu Kyi herself has made efforts to defrost relations with the military leaders, writing twice to junta leader Than Shwe since September to offer help in getting Western economic sanctions lifted and asking to meet with him.

The government's official liaison officer met with Suu Kyi in January - the fourth meeting since last September as both sides tentatively renew dialogue.

Last November the authorities allowed her to make a rare appearance in front of the media after she held talks with US Assistant Secretary of State Kurt Campbell, the most senior Washington official to visit Myanmar for 14 years.

The administration of US President Barack Obama has been pursuing greater engagement with the Myanmar regime after deciding that sanctions alone were not working.

Myanmar has been ruled by the military since 1962.