WASHINGTON — Just a year after his administration signaled it would help Myanmar emerge from decades of repressive military rule, President Barack Obama will make history Monday by becoming the first U.S. president to visit the long-isolated Southeast Asian nation.

Obama's gesture, the centerpiece of a four-day trip to the region that will include stops in Thailand and Cambodia, comes as the White House seeks to send another strong message that it is serious about its "pivot to Asia" — a rebalancing of U.S. military and economic interests after more than a decade of war in the Middle East.

During his six hours in Myanmar, also known as Burma, Obama is scheduled to meet separately with President Thein Sein and democracy leader Aung San Suu Kyi, whose release in 2010 after 15 years under house arrest launched her nation's opening to the West. She has since become a member of parliament.

Administration officials said Obama intends to hail the country's "remarkable progress" toward democratic rule during a speech at Yangon University in Myanmar's historic capital but also to push its leaders farther along the path of reform, mindful that the nascent effort remains fragile.

"We are not naive to this. We understand the dangers of backsliding, and if it happens, we'll take note of it," said the White House national security adviser, Thomas Donilon, on Thursday in Washington. "There's a lot more work to do, but it's a moment when the president really can attempt to lock in the progress that has been made and give a tremendous boost to the reform movement in Burma."

Buffeted by criticism of its Middle East policy after recent setbacks to the Arab Spring democracy movement, the administration hopes Obama's visit to Southeast Asia will jump-start his second-term foreign policy agenda as the United States seeks to counterbalance China's growing influence.

Obama will meet with Thailand's prime minister, Yingluck Shinawatra, and in Cambodia he will attend a gathering of the Association of Southeast Asian Nations and participate in this year's East Asia Summit to discuss security issues. Obama is also expected to meet privately with several foreign leaders, including Chinese Premier Wen Jiabao and Japanese Prime Minister Yoshihiko Noda.

Ben Rhodes, the deputy national security adviser for strategic communication, called the renewed Asia focus a "critical part of the president's second term and ultimately his foreign policy legacy."

He added, "We see this as an opportunity to dramatically increase U.S. exports and to increase U.S. leadership in the fastest-growing part of the world."

But in betting on Myanmar, where the United States installed an ambassador in June for the first time in more than two decades, the White House has opened itself to criticism that it is taking a victory lap on Asia too quickly. Leading human rights organizations have lobbied hard against Obama's visits to Myanmar and Cambodia because of what they say are ongoing abuses by their governments.

In Myanmar, the activists cite ethnic violence against the Muslim minority that has left hundreds dead and up to 100,000 people displaced. They warn that the Obama administration is rewarding the government for modest reforms without any tangible new commitments to show for it.

"They believe in the magical power of an event and an address," said John Sifton, Asia advocacy director at Human Rights Watch. "But this trip is premature and undeserved. Why are they going? I do not know a legitimate reason."

Obama's itinerary

Thailand:On his first stop, Obama will meet with Prime Minister Yingluck Shinawatra to mark 180 years of diplomatic relations between the two nations.

Myanmar: During a brief stop Monday, Obama will meet with opposition leader Aung San Suu Kyi and President Thein Sein, and deliver an address in which he will call for continued political reforms.

Cambodia: Obama will participate in the East Asia Summit. He will hold separate one-on-one meetings with outgoing Chinese Premier Wen Jiabao and Japanese Prime Minister Yoshihiko Noda.