Thein Sein plans landmark Washington visit (Click to view website)

Myanmar's leader plans a landmark visit to Washington this month, a source said Thursday, as the United States eased visa restrictions in a sign of support despite a surge in anti-Muslim violence.

President Thein Sein, who would be the first leader of the country to visit in half a century, is planning to be in the American capital around May 20 or May 21, a staff member at the US Congress told AFP on condition of anonymity.

The trip would include a summit with President Barack Obama at the White House. Administration officials said they had no announcement to make but have previously said that they were studying a visit by Thein Sein.

In another step towards thawing relations, Secretary of State John Kerry on Thursday ended a 1996 ban on US visas to Myanmar nationals accused of hindering democracy during the country's decades of harsh military rule.

Separate restrictions remain on visas for nationals accused of human rights violations. A State Department official said the 1996 ban was overly broad by including government workers, officers and even some pensioners.

"Clearly many people in those categories are now contributing to the reform process and need to engage" through visits to the United States, the official told reporters on condition of anonymity.

The US decisions recognize "the important changes the government of Burma has made and encourage and empower the government and the people of Burma to continue on the path of political and economic reform," he said.

The congressional source said the administration was considering further steps during Thein Sein's visit, such as starting to call the nation Myanmar, the leadership's preferred usage, and not the earlier name of Burma favored by exile groups.

The United States is also looking at whether to include Myanmar in the Generalized System of Preferences, through which it offers duty-free access for up to 5,000 products from developing countries that meet labor standards.

Obama paid his own visit to Myanmar in November, when he praised the nation for its transition but called for progress on reforms, particularly in the treatment of ethnic minorities.

But Thein Sein's visit is expected to be controversial due to a surge in violence against the Rohingya, a Muslim people who are not considered citizens by Myanmar.

A recent Human Rights Watch study accused Myanmar of a "campaign of ethnic cleansing" against the Rohingya, saying that at least 211 have been killed since June 2012 and tens of thousands more forcibly displaced.

Jennifer Quigley, executive director of the US Campaign for Burma, a Washington-based pressure group, accused the Obama administration of only responding to positive developments and not to setbacks.

"To invite him at this point of time would really just reinforce the message of a positive relationship when there really has been no move by the US government to tie this to the Burmese government taking necessary steps" to curb the violence, she said.

It would be the first visit to Washington by a head of the country since military leader Ne Win was invited in 1966 by president Lyndon Johnson.

Thein Sein has previously visited the United States to attend the UN General Assembly, but only held meetings in New York.

A former general, Thein Sein surprised even many skeptics by launching a raft of reforms after taking office in 2011 as a nominal civilian, including freeing political prisoners and relaxing censorship.

He has allowed opposition icon Aung San Suu Kyi to take a seat in parliament, a once unthinkable gesture as the Nobel Peace laureate spent most of the previous two decades under house arrest.

While Obama has suspended most sanctions, he issued a declaration on Thursday that keeps measures on the books, allowing the United States to reimpose them in response to setbacks.

The European Union last week dropped virtually all of its sanctions against Myanmar with the exception of a military embargo.

Asian nations already conducted business with Myanmar, which became a close partner of neighboring China while under Western sanctions.