Lawyers for Burmese opposition leader Aung San Suu Kyi urged the country's highest court Wednesday to reverse a ban on two key defence witnesses at her trial.

Burmese opposition leader Aung San Suu Kyi is seen in this 1996 file photo. (Richard Vogel/Associated Press)

The High Court of the country also known as Myanmar did not immediately set a date for its ruling.

Suu Kyi's widely watched trial is set to resume Friday, but is expected to be delayed pending the appeals decision, said defence lawyer Nyan Win.

Suu Kyi faces up to five years in prison if convicted of violating her house arrest after an uninvited American man swam to her lakeshore home and stayed for two days.

The Nobel laureate has spent 13 of the past 19 years in detention, mostly under house arrest.

The court presiding over the trial at Insein Prison in Burma's largest city, Rangoon, has allowed only one of four defence witnesses to take the stand. On appeal, the Rangoon divisional court ruled that a second witness could be heard.

Lawyers on Wednesday were pursuing a second and final appeal to reinstate the remaining two barred witnesses, Win Tin and Tin Oo, both senior members of Suu Kyi's National League for Democracy.

Security was tight outside the courthouse, with 20 truckloads of armed riot police stationed nearby and another half-dozen circling downtown Rangoon, the commercial capital.

Prosecutors argued that Win Tin, a prominent former journalist and ex-political prisoner, should not be allowed to testify because he is critical of the government and often gave interviews to foreign media, said Nyan Win.

The defence team argued there was no law in the tightly ruled country that bars court testimony from government critics, according to Suu Kyi's lawyer.

Suu Kyi's trial has drawn outrage from the international community and local supporters, who say the military government is using the bizarre incident as an excuse to keep her detained through next year's elections.