A US senator met Myanmar's top general and opposition leader Aung San Suu Kyi, while arranging the release of an American prisoner on a weekend mission that offered a rare opening for better ties with the isolated nation.

Democratic Senator Jim Webb told reporters at the airport in Yangon on Sunday he was leaving Myanmar with John Yettaw, whose swim to Suu Kyi's home in May led to her renewed detention.

He met Myanmar's junta leader, Than Shwe, at the remote new capital of Naypyidaw on Saturday and then flew to Yangon to meet with Suu Kyi at a guesthouse immediately afterward.

Webb said he also asked for Suu Kyi to be released. Asked about the junta's response, he repled: 'I'm hopeful about this.'    

Yettaw did not attend the news conference. A police officer told Reuters he had been taken from prison to the airport, where he joined the senator's party. Their plane left Yangon for Bangkok at around 1:30 p.m. (0700 GMT).

Webb was allowed by the military authorities to speak with Suu Kyi for about 45 minutes at a guesthouse in Yangon, after earlier meeting members of her National League for Democracy (NLD) and other political parties who had been invited to Naypyidaw by the government.

'He wanted to know the opinions of political parties about the present situation,' 88-year-old NLD senior leader Than Tun, who was present at the meeting, told Reuters on Sunday.

'We think his visit will be somewhat conducive to working for national reconciliation in our country.'    

Other observers remained bitter at the treatment of Suu Kyi.

'The most tangible outcome of his visit is the release of John Yettaw, who caused the mess,' said Thakhin Chan Tun, a former ambassador to North Korea. 'However, Daw Aung San Suu Kyi, who is completely innocent in this incident, is still under house arrest.'    

Mymanmar's military authorities said Yettaw's two-day stay in Suu Kyi's home breached the terms of her house arrest, which led to her trial.

She was sentenced last week to another 18 months under house arrest, enough to keep her out of campaigning for elections due next year. Some critics say this was the junta's intention, and that Yettaw's escapade provided the excuse for the new trial.

Yettaw himself was sentenced to seven years' hard labour in a parallel trial on three charges, including immigration offences and 'swimming in a non-swimming area'. His health is fragile and he spent several days in hospital this month.

Suu Kyi has championed the fight for democracy in the former Burma and has spent 14 of the past 20 years in detention of one form or another.

US President Barack Obama said her conviction violated universal principles of human rights and called for her release.

In May, Obama extended a ban on US investment in Myanmar imposed in 1997 because of the authorities' political repression. He has also renewed sanctions on imports from Myanmar.

Before Suu Kyi's trial ended, US Secretary of State Hillary Clinton held out the prospect of better relations with Myanmar but made that conditional, among other things, on the release of Suu Kyi and other political prisoners.

Webb, a Democrat who is chairman of a Senate subcommittee on East Asia and Pacific, is the first member of Congress to travel in an official capacity to Myanmar in more than a decade.

His office said on Saturday he was 'the first American leader ever to meet with Myanmar President Than Shwe'.

A former Navy Secretary and a Vietnam War veteran who speaks Vietnamese, Webb favours a policy of engagement with the junta.

The United States has for years backed sanctions to persuade the generals to release political prisoners, to little effect.

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