By Louis Charbonneau

YANGON, MYANMAR - U.N. Secretary-General Ban Ki-moon says he has a "tough mission" when he meets Myanmar's top general Friday to urge the junta supremo to free all political prisoners and ensure next year's elections are credible.

Ban said on arrival in Yangon he would ask Senior General Than Shwe when they meet in the country's new capital, Naypyidaw, to allow him to see opposition leader Aung San Suu Kyi, whose trial was adjourned earlier Friday.

"I'm going to urge (the generals) to accelerate their political process ... and release all political prisoners, including Aung San Suu Kyi," Ban told reporters.

He said he would convey international concern about Suu Kyi's trial and press the regime to ensure next year's planned multi-party elections are credible and transparent.

"The genuine will of the Myanmar people should be reflected," Ban said.

The stakes are high for Ban and the risk of failure great.

Halfway through a five-year term at the helm of the United Nations, Ban has faced a wave of criticism from detractors who say his low-key approach to the job does not work. He is eager to prove them wrong, U.N. diplomats say.

Ban made clear he was under no illusions about how difficult it would be to persuade the military junta in the former Burma to free prisoners and take concrete steps toward democracy ahead of next year's multi-party elections.

"We must try our best to bring changes, he told reporters in Singapore before departing for Myanmar.

"I'll do my best (but) I do not believe my visit should be a make-or-break event... This will be a very difficult mission."

MEANINGFUL DIALOGUE

He said he would also press Than Shwe and Prime Minister Thein Sein to engage in "meaningful and credible dialogue" with Suu Kyi and the opposition.

Ban said he would meet with representatives of "registered political parties" in Naypyidaw, including Suu Kyi's National League for Democracy.

However, Suu Kyi herself will not be at that meeting and it was not clear if Ban would be able to meet her at all.

She has spent 14 of the past 20 years in detention, mostly under house arrest at her lakeside home in Yangon. It will be up to Than Shwe whether Ban sees her.

Her lawyer said her trial had been postponed until July 10, apparently because the Supreme Court did not send the case files to the North Yangon District Court, where Suu Kyi appeared Friday.

"Daw Aung San Suu Kyi expressed her surprise that this happened," Nyan Win told reporters.

The Nobel laureate, 64, was charged with violating the terms of her house arrest by allowing an American intruder to stay at her home in May, which prosecutors say breached a security law designed to thwart "subversive elements."

However, critics say the charges are trumped up and that the trial is an attempt to keep Suu Kyi out of the elections next year, which are expected to entrench nearly half a century of army rule.

Human rights groups are watching Ban's moves closely. According to several U.N. diplomats, New York-based Human Rights Watch advised Ban not to accept the junta's invitation, warning him it could be used for propaganda purposes.

But Ban, the diplomats said, decided to go anyway, hoping his presence and knack for quiet diplomacy would persuade the generals to compromise, as they did last year when Ban convinced them to lift restrictions on the delivery of humanitarian aid to victims of Cyclone Nargis.

Analysts say Ban may have been given some indication by the generals, or by U.N. envoy Ibrahim Gambari after his trip last week, that his visit might bring some kind of positive result.

Human Rights Watch said Ban "should not accept the return of opposition leader Aung San Suu Kyi to house arrest or vague statements about political reform as signs of a successful visit."

"If no commitments for reform are made, Ban should clearly and publicly state that a process that mocks the very idea of fundamental freedoms and democracy will have no legitimacy," it said in a statement. --REUTERS