Free Aung San Suu Kyi

Mr Obama delivered the message as he met leaders of the Asean grouping of south-east Asian nations in Singapore.

White House press secretary said Mr Obama raised the issue "directly" with General Thein Sein.

Ms Suu Kyi's house arrest was extended in August beyond the elections planned for next year. She has spent 14 years in detention in the past two decades.

Lawyers for Ms Suu Kyi, a Nobel peace prize laureate, have lodged an appeal with the Supreme Court against her extended house arrest.

The Apec summit brings together leaders of the 10-member Association of South East Asian Nations (Asean), which includes Burma.

Cautious engagement

Before the closed talks in a hotel room, Mr Obama and the Asean leaders stood in a line on a stage, crossing their arms to shake hands with the leader on either side.

Gen Thein Sein was not close to Mr Obama - a direct meeting would have marked the first time in 43 years a US president had met a Burmese leader.

But the fact that a US president has sat down at the same table with a member of the Burmese military government is a clear sign that America is serious about wanting to re-engage with the region, says the BBC's Rachel Harvey in Singapore.

US presidents have previously refused to hold meetings with Asean when Burmese leaders were present.

The US has previously boycotted Asean meetings because of Burma.

"The president was just - as you know - in the scheduled meeting with the 10 Asean nations, and brought up in the meeting the... release of Aung San Suu Kyi by Burma. So, he brought that up directly with that government," Mr Obama's spokesman, Robert Gibbs said.

A joint statement released after the US-Asean talks, welcomed Mr Obama's policy of engagement with Burma and "underscored the importance of national reconciliation" there, but did not mention Aung San Suu Kyi.

"The general elections to be held in Myanmar in 2010 must be conducted in a free, fair, inclusive and transparent manner in order to be credible to the international community," the statement said.

Aung San Suu Kyi's party won Burma's last elections in 1990 but the military never allowed her to take power.

Observers believe Burma's authorities want to keep the pro-democracy leader in detention until after polls scheduled for next year.

The Obama administration has said it favours cautious diplomatic engagement, with sanctions against the regime remaining in place until real progress on democratic change is made.