After a lull in the U.S.-Burmese relationship, the past few weeks have seen the defection of a top-ranking Burmese diplomat to the United States, the confirmation hearing of a new U.S. envoy to Burma, and opposition leader Aung San Suu Kyi’s first travels outside Rangoon since her release from house arrest last year.

According to Aung Din, a former Burmese political prisoner who helped draft the letter to Obama, the coalition of human rights activists hopes to push U.S. officials toward a tougher stance against the military-controlled government.

“The U.S. has been trying this same policy of engagement for two years already,” said Aung Din, director of U.S. Campaign for Burma. “But such engagement should be time-bound and with clear benchmarks and combined with stronger pressure.”

The letter was signed by organizations including Human Rights Watch and the Carter Center, as well as pro-labor and pro-student activist groups such as the AFL-CIO and the American Federation of Teachers.

It calls on the Obama administration to support two specific measures against Burma, also known as Myanmar: banking sanctions against similar to those that were imposed against Libya and a United Nations commission of inquiry to investigate war crimes and human rights abuses.

Since the Obama administration launched talks with Burma in 2009, it has sent various State Department officials to the country. The official awaiting confirmation as new special envoy, Derek Mitchell, would be the first U.S. coordinator for policy for Burma.

At his confirmation hearing, Mitchell, who is currently a senior defense official, said that he plans to coordinate more with international allies to establish a cohesive diplomatic approach in dealing with Burma.

“To date, in my view, the inability of key members of the Burma-interested community around the world to coordinate their approach to Burma has only undermined the effective realization of shared objectives,” he said.

Another flash point could come later this month at the meeting of the Association of South East Asian Nations, or ASEAN. The chairmanship and hosting of the ASEAN meeting rotates every year, and Burma being considered as host for 2014.

U.S. officials have been leery of weighing in on the issue, but at his confirmation hearing, Mitchell said, “I think, frankly, where Burma is today, ASEAN recognizes that Burma is an outlier and is somewhat of an embarrassment to the organization.... I think Burma has some work to do in order to make ASEAN nations comfortable with that — and the rest of the international community.”

Secretary of State Hillary Rodham Clinton is traveling to Indonesia for the ASEAN meeting, where the Burmese chairmanship issue may be decided.