A group of influential human rights organizations says the U.S. may be moving too quickly in relaxing sanctions against Burma.

The group, which includes Human Rights Watch and seven other U.S.-based organizations, sent a letter to President Barack Obama on Tuesday, questioning his administration's decision to ease several long-standing sanctions against Burma earlier this month.

The U.S. eased an investment ban, some travel restrictions, and other sanctions in early April after Burma held by-elections in which pro-democracy leader Aung San Suu Kyi's political party won 43 of the 44 seats it contested.

The letter says any further easing of the sanctions should come only after additional political reforms, including the release of more political prisoners, and end to conflicts with ethnic rebel groups and amendments to Burma's military-drafted constitution.

Other groups that signed the letter include Physicians for Human Rights, Open Society Foundations and the AFL-CIO, the largest federation of American labor unions.

While the American groups remain leery about any easing of sanctions, Burma's neighbors are welcoming the moves, which promise to provide a much-needed boost to Burma's economy. In a formal statement Wednesday, the Association of South East Asian Nations (ASEAN) hails Europe's decision to suspend most sanctions for a year as “the right thing to do at the right time.”

The EU said Monday that it will suspend almost all sanctions with the exception of an arms embargo.

Burma's current military-backed civilian government has undertaken a series of dramatic political reforms since taking power last March, including the release of hundreds of political prisoners, the holding of peace talks with ethnic rebels and the allowance of greater press freedoms.

United Nations Secretary-General Ban Ki-moon will travel to Burma later this week to observe the country's transition from military dictatorship.