It is Gambari's eighth visit to Myanmar, none of which have so far been able to nudge the country's ruling generals towards significant reform or the release of prominent political prisoners, such as Aung San Suu Kyi.

'Appropriate timing'

Activists continue to call for the UN to assist in the release of Aung San Suu Kyi [EPA]
According to UN officials Gambari is to brief Ban Ki-moon, the UN secretary-general, on the outcome of his mission and Ban will then decide whether to go ahead with plans to visit Myanmar early next month

As Gambari left for Yangon on Wednesday, Ban told the Associated Press he was considering the "appropriate timing" for a visit for face-to-face talks with the country's top general, Than Shwe.

The UN boss and Gambari have been trying to persuade Myanmar's ruling generals to free all political detainees and to steer their country on the path to democracy and national reconciliation.

Aung San Suu Kyi is being held in jail on charges of violating the terms of her house arrest after an American man, John Yettaw, swam to her lakeside house earlier this year.

She faces up to five years in jail if convicted. Myanmar officials have said her trial is expected to resume in early July.

She has spent 13 of the past 19 years in detention since the government refused to recognise the landslide victory of her National League for Democracy party in 1990 elections.

Myanmar opposition supporters have condemned her jailing as an effort to keep her in detention during elections the government has scheduled for next year as part of what it calls its "road map to democracy".

The vote, expected to take place some time in 2010, has been dismissed by critics as a sham designed to cement the military's continued grip on power behind a veneer of democracy.