HANOI, Vietnam — Southeast Asia's top diplomats confronted Myanmar by demanding that democracy icon Aung San Suu Kyi be freed before the country's elections next month, while the U.N. chief warned Thursday that keeping thousands of political prisoners locked up could destroy the vote's credibility.

Despite persistent pressure, Myanmar officials gave no clear answer about the fate of Suu Kyi, who has spent 15 of the past 21 years imprisoned or under house arrest.

But Myanmar confirmed that its military leader, Than Shwe, will not run in the Nov. 7 elections as the military regime attempted to present a new image to the world at a regional summit that opened Thursday in Vietnam.

U.N. Secretary-General Ban Ki-moon told The Associated Press that by freeing its jailed dissidents, Myanmar could create a "perception that this election will be more inclusive," even if it's too late for the dissidents to run as candidates or to vote.

The Southeast Asian country's military rulers have enacted laws that prevent Suu Kyi and other political prisoners from contesting the elections. That leaves the junta-backed party as its only strong contender, leading critics to accuse the regime of maneuvering to ensure that the military will remain in control.

"Without releasing all political prisoners, then there may certainly be some issue of legitimacy or credibility," Ban told the AP in an interview in Phnom Penh, Cambodia.

He spoke before flying to Hanoi, where he was to meet with Myanmar Prime Minister Gen. Thein Sein (pronounced "Tane Sane") on the sidelines of the summit. Although Thein Sein represents his country at international events, he takes his orders from junta leader Than Shwe.

Myanmar officials refused to directly confirm whether Suu Kyi would be released from house arrest when her detention expires on Nov. 13.

"Now at this time I would strongly urge the Myanmar authorities that it is not too late — even at this time — to release all political prisoners so that the Nov. 7 elections could be more inclusive and more participatory and credible," Ban said.

During a meeting with Myanmar's prime minister, Philippine President Benigno Aquino III pressed for Suu Kyi's immediate release, said presidential spokesman Ricky Carandang.

"There was no commitment and the president, I would say, was disappointed at the lack of response," he said.

But Indonesian Foreign Minister Marty Natalegawa said Myanmar also did not contest that her detention ends just after the elections, suggesting that perhaps she may be freed.

In Washington, State Department spokesman P.J. Crowley dismissed the idea that hints of Suu Kyi's release signaled anything but business-as-usual for the regime.

"This is a craven manipulation by Burma," Crowley said. "How convenient that they're hinting that she might be released after an election that is unlikely to be fair, free or credible."

Suu Kyi's party is boycotting the elections as undemocratic after winning a landslide victory in the country's last elections in 1990. The junta refused to accept those results.

Philippine Foreign Secretary Alberto Romulo said Myanmar Foreign Minister Nyan Win announced that junta chief Than Shwe will not be on the ballot — the first confirmation from the reclusive government that the longtime military leader will not participate in the polls. However, he is widely expected to have some new role after the elections.

"You know the system they have. He will be elected president, I'm almost sure," Romulo said.

The military junta, which has been in control for the past five decades, worked to put on a fresh face at the Hanoi meeting, unveiling a redesigned flag and new name — the former "Union of Myanmar" is now the "Republic of the Union of Myanmar."

Such changes, critics say, are intended to mask the shortcomings of the long-awaited polls.

Another issue high on the summit agenda involves territorial disputes on the high seas between China and its neighbors.

China claims sovereignty over the entire South China Sea, but parts of it are also claimed by several of its Southeast Asian neighbors, including Vietnam. China recently clashed with Japan over a ship collision in the East China Sea, straining relations and stoking anti-Japanese protests.

Heads of state from the Asean countries — Brunei, Cambodia, Indonesia, Laos, Malaysia, Myanmar, the Philippines, Singapore, Thailand and Vietnam — along with leaders from Australia, China, India, Japan, South Korea, New Zealand, Russia and the United States will attend the summit. (AP)