Lawyers for detained Burmese opposition leader Aung San Suu Kyi say a court has agreed to hear their appeal against a conviction that extended her house arrest by 18 months.

Lawyer Nyan Win said Friday the Divisional Court agreed to hear the appeal on Sept. 18.

A lower court ruled Aug. 11 that the 64-year-old Nobel Peace Prize laureate was guilty of violating the terms of her earlier detention after an uninvited American visitor stayed at her home. She was sentenced to serve an additional 18 months of house arrest.

The case drew international condemnation and renewed calls for Suu Kyi's freedom. Suu Kyi has spent 14 of the last 20 years in detention.

Burma's opposition leader Aung San Suu Kyi, shown in this 2002 file photo, is appealing a criminal conviction that put her under house arrest for 18 more months. (David Longstreath/Associated Press)"We submit the appeal because the judgment against Daw Aung San Suu Kyi was wrongful," lawyer Nyan Win said. Daw is a respectful term for a woman.

Suu Kyi earlier described the conviction as unfair and the court's assessment of the case as unjust.

The appeal argues that the law cited by authorities is invalid because it applies to a constitution abolished two decades ago, head lawyer Kyi Win said.

The defence team will separately appeal the convictions of two female companions who live with Suu Kyi.

Suu Kyi and her two companions returned to her tightly guarded home the day she was convicted. She has been detained for about 14 of the past 20 years for her nonviolent political activities, but this was the first time she faced criminal charges.

The American, John Yettaw, was sentenced to seven years in prison but was released on humanitarian grounds and deported Aug. 16.

Suu Kyi's sentence ensures she cannot participate in elections scheduled for next year. Her party swept the last elections in 1990 but the results were never honoured by the military, which has ruled Burma — also known as Myanmar — since 1962.