In Burma's remote capital, President Barack Obama will confront a nation backsliding in its pledges to enact economic and political reforms that were rewarded with U.S. sanctions relief and made the long-isolated country a darling of Obama's efforts to stake out a legacy in Asia.

The optimism over Burma's unexpected shift from military rule has subsided as reforms slow. The country's pro-democracy hero Aung San Suu Kyi remains ineligible for next year's presidential elections because of constitutional rules designed to block her. And Burma's minority Rohingya Muslims face escalated attacks and persecution in the largely Buddhist nation.

"There's no certainty about the future," said Derek Mitchell, the U.S. ambassador to Burma. "There's nothing inevitable about this all succeeding."

Obama arrived Wednesday night in the capital of Naypitaw, his second stop on an eight-day Asia-Pacific swing that opened in China and ends later this week in Australia. The president was first attending a pair of regional summits, then holding talks in the capital with Burma's President Thein Sein before traveling on to Yangon to meet with Suu Kyi.

White House officials say Obama has always been realistic about the challenges ahead in Burma, a country that in many cases lacks the infrastructure and capacity to enact the reforms its leaders have promised. However, human rights advocates and other critics of the administration's policy toward Burma say the U.S. gave up its leverage by too quickly rewarding the government for reforms it has not yet fulfilled.

In a written interview with Burma's The Irrawaddy magazine, Obama acknowledged that progress has been slower than many had hoped. He said that in some instances, the country has even taken steps backward, citing restrictions on former political prisoners, detention of journalists and the treatment of Rohingya Muslims. Obama said a key message on his trip would be that Burma's government must protect the safety of all of its inhabitants.

"I've always been clear-eyed about how difficult this transition would be," Obama said. "But as president, I'm determined that the United States will remain a partner with those who seek greater freedom, prosperity and dignity."

Michael Green, an Asia analyst at the Center for Strategic and International Studies, said the White House put reforms in Burma "on the scoreboard and they dropped it and now they're scrambling."

For Obama, the pursuit of democracy in Burma has become a centerpiece of his efforts to deepen U.S. engagement in Asia. In 2012, he became the first sitting U.S. president to visit the country, a daylong stop that included an emotional meeting with Suu Kyi at the residence where she spent more than a decade under house arrest. The president's advisers still recall the thick crowds that lined the streets to watch Obama's motorcade speed through the streets, defying rules that had limited large public gatherings.

It's unlikely Obama would be returning to Burma ahead of next year's election if the country weren't hosting the two regional summits. Still, White House aides say the timing of the trip gives Obama an opportunity to make an in-person appeal for progress.

"The United States can best move that forward by engagement," said Ben Rhodes, Obama's deputy national security adviser. "If we disengage, frankly I think that there's a vacuum that could potentially be filled by bad actors."