A leading U.S.-based rights group has condemned the recent merger of a powerful Burmese mass movement that supports the country's ruling junta into the army's new political party, a move critics say is designed to ensure the military government dominates national elections expected later this year.

Human Rights Watch Monday called the government's decision to allow the Union Solidarity and Development Association, or USDA, to disband and transfer its assets to a new party formed by senior members of the junta "a brazen distortion of the electoral process."

The new party, the Union Solidarity and Development Party, or USDP, was formed in April when Prime Minister Thein Sein and 26 senior officers and ministers resigned their military commissions so they could run in the upcoming elections.

The junta's critics say any transfers of the movement's state-owned property or funds would violate electoral laws and show outright government support for USDP, adding further controversy to an already disputed election.

Human Rights Watch says the military junta has long used the USDA for partisan political purposes.

The movement - said to have more than 24 million members, many of whom were conscripted - has been implicated in the violent suppression of protests led by Buddhist monks in 2007, and in multiple attacks on opposition leader Aung San Suu Kyi. The USDA was formed in 1993 and owns swathes of property across the country. Its vast membership base has generated sizable wealth.

Last week, the U.S. State Department repeated its call for Burma to free political prisoners, including democracy leader Aung San Suu Kyi, and enact democratic reforms. U.S. Assistant Secretary of State for East Asian and Pacific Affairs Kurt Campbell said recent Burmese actions suggest the upcoming election will not be free and fair.

Burma's new election laws bar Aung San Suu Kyi from running for office since parties with members who are currently serving a prison term or detention order are prohibited. Her party, the National League for Democracy, has called the laws unfair and undemocratic.

Authorities have kept the Nobel Peace Prize laureate under some form of detention for 14 of the last 20 years.  Thousands of opposition activists and others critical of the government have also been jailed. Amnesty International last week said the Association of Southeast Asian Nations, or ASEAN, should demand Burma unconditionally release all prisoners of conscience.

The military junta has ruled Burma since 1962. The elections would be the first since 1990, when the NLD won a decisive victory. The military government refused to recognize the results.