But the administration made it clear that the improved trade and engagement implied by its diplomatic gesture was conditioned on further advances by Myanmar's government in restoring civil rights and democratic institutions.

"As an iron fist has unclenched in Burma, we have extended our hand, and are entering a new phase in our engagement on behalf of a more democratic and prosperous future for the Burmese people," the announcement from the White House said.

The White House announced the nomination of Derek Mitchell, who has been the lead architect in the warming of relations with the country also known as Burma, saying the move was in recognition of Myanmar's "significant progress along the path to democracy."

Heralding reform in Myanmar but warning of much work still ahead, the Obama administration on Thursday named its first full ambassador to the Southeast Asian nation in 22 years.

The restoration of a top envoy was in recognition of the strides forward made by the military-backed leadership in holding parliamentary elections last month that led to "the sight of Aung San Suu Kyi being sworn into office after years of struggle," the White House said in a statement.

"Of course, there is far more to be done. The United States remains concerned about Burma’s closed political system, its treatment of minorities and detention of political prisoners, and its relationship with North Korea," the statement said.

"We will work to establish a framework for responsible investment from the United States that encourages transparency and oversight and helps ensure that those who abuse human rights, engage in corruption, interfere with the peace process, or obstruct the reform process do not benefit from increased engagement with the United States."

The European Union last month lifted economic sanctions on Myanmar in recognition of recent reforms undertaken by President Thein Sein. Suu Kyi, the longtime democracy activist who spent much of the last two decades under house arrest for challenging the authoritarian regime, plans to visit Europe next month, a sign of trust in the political reforms underway in her homeland.

Secretary of State Hillary Rodham Clinton made a historic visit to Myanmar late last year to signal Washington's interest in re-engaging with the geopolitically strategic and resource-rich country that is more closely aligned with China.

Mitchell, 47, was named by Obama last year as special representative and policy coordinator for Myanmar. His appointment must still be confirmed by the Senate.

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--Carol J. Williams in Los Angeles

Photo: Opposition leader Aung San Suu Kyi, center, at "The Burmese Way to Democracy" photo exhibit in Yangon on Thursday. She plans her first trip out of Myanmar in two decades next month. Credit: Khin Maung Win / Associated Press