BANGKOK: In the first-ever encounter between a senior US official and the junta strongman, Democratic Senator Jim Webb is due to meet Myanmar supremo Than Shwe later this week, Webb's office said Thursday.

The visit by Webb, who is close to US President Barack Obama, comes after the junta was widely condemned for extending democracy leader Aung San Suu Kyi's house arrest for another 18 months.

"Later this week, US Senator Jim Webb is scheduled to meet with leaders at the highest levels of the national government in Burma (Myanmar), including Senior General Than Shwe," a statement from Webb's office said.

"If the Shwe meeting takes place it will be the first time that a senior American official has ever met with Burma's top leader," it said, noting also that no member of Congress has visited Myanmar in over a decade.

One of the most high profile visits by a US official in recent years was that of William Berger, head of a US disaster assistance team, who delivered a planeload of aid to Yangon after Cyclone Nargis in May 2008.

Webb, who arrived in Laos Thursday to kick off a two-week tour of Southeast Asia, is scheduled to visit Myanmar this weekend.

"It is vitally important that the United States re-engage with Southeast Asia at all levels," Webb said in a statement announcing his arrival in the Lao capital Vientiane, where he was due to hold a press briefing Thursday.

Also convicted along with Suu Kyi was US citizen John Yettaw, who triggered her latest trial with a bizarre incident in May when he swam to her lakeside house in Yangon.

The 54-year-old US military veteran, who is an epileptic and diabetic, was sentenced to seven years of hard labour and imprisonment.

Obama demanded Yettaw's immediate release, along with Suu Kyi's and that of thousands of political prisoners held in Myanmar's notorious jails ahead of elections scheduled for next year.

Webb -- a hard-nosed Vietnam War veteran who chairs the Senate Foreign Relations subcommittee on East Asia and Pacific affairs -- was also to visit Thailand, Vietnam and Cambodia over his two-week tour.

The senator, a former Republican defence official who has authored military works, was seen as a potential vice presidential pick for Obama during last year's US election campaign but was quick to rule himself out of the running.

Myanmar researcher David Mathieson of Human Rights Watch said it was "significant" that Than Shwe had agreed to meet Webb, given the military ruler's "distrust and xenophobia".

"I think Than Shwe will probably appreciate Webb's military background and his seniority," he told AFP, but he warned "obviously Than Shwe will try and turn it to his advantage".

Than Shwe, who assumed power in 1992, has long been considered a bete noire to the US, which along with the EU has imposed sanctions against the regime.

Mathieson said he "wouldn't be surprised" if Webb tried to secure Yettaw's release from Myanmar, but noted the senator's visit was "just good timing" in this respect, because he had been trying to visit the country for a few months.

Yettaw's lawyer Khin Maung Oo said Wednesday that they would appeal against his sentence and if necessary urge Than Shwe to deport him.