Secretary of State Hillary Rodham Clinton met with Burmese President Thein Sein in Burma in December. (Saul Loeb — Associated Press)

The reason is plain: President Thein Sein believes that, with Burma’s release of political prisoners, its scheduling of elections and its tentative softening toward opposition leader Aung San Suu Kyi, Burma has done its part. Now is the time for the West to lift sanctions.

“It has been nearly 20 years now,” Thein Sein told The Post’s Lally Weymouth. “I would like to see them ease  … and eventually get rid of the sanctions.”

The problem is that U.S. officials and Congress aren’t willing to take that step without further proof that Burma’s recent reforms are more than just a sleight of hand.

In a sign of good faith, the Obama administration has tried to dole out diplomatic rewards to the repressive government – sending Secretary of State Hillary Rodham Clinton for a visit and promising to dispatch the first U.S. ambassador to the country in years. There might be other small steps the administration could take. The question is whether those will be enough to keep Burma, also known as Myanmar, moving in the right direction.

“The administration has a difficult job calibrating a response,” said Michael Green, a former senior adviser for Asia on the National Security Council and now an adviser at the Center for Strategic and International Studies. “They could open a USAID mission there to signal possible future aid. There’s a whole slate of military-to-military things you could do, like offering their military leaders training on the Hawaii base, as we do with other Asian countries.”

Senior officials in the Obama administration confirm that any move to lift sanctions remains pretty far off, even as they try to buy time diplomatically to see just how committed Burma’s leaders are to reform.

Among other developments, they want to see how upcoming April 1 elections play out and whether international observers are invited in, as well as whether the government can establish some permanent institutional fixtures, such as an independent judiciary.

Most of all, they want to see a solution to the ongoing and bloody fighting between the Burmese army and the various armed ethnic groups along the country’s border regions.

Ethnic fighting is “the biggest, defining issue for the country’s future,” said one senior administration official, an assessment that echoes similar recent comments by dissident leader Suu Kyi.

While the government has recently brokered a temporary ceasefire with the Karin group, heavy fighting continues with the Kachin in the northeast. Human rights activists say Burmese troops continue to use rape as a weapon of war and have burned and looted homes in villages that oppose the military-backed government.

“In the long view of things, nothing, none of this progress can be sustained without a solution to the ethnic problem,” said the senior U.S. official.