Sen. Mitch McConnell also called on the European Union to make clear that Myanmar’s chairmanship “is completely unacceptable.”

McConnell is one of the top voices on foreign affairs in Congress. He is the No. 2 Republican in the Senate and chairs the subcommittee that funds State Department operations and foreign assistance.

He has been the leading congressional critic of the military government in Myanmar, also known as Burma, and his views carry considerable weight on the issue with the administration of President George W. Bush, a fellow Republican.

In a statement to The Associated Press, McConnell said he was “disturbed that our close ally Thailand continues to fully and unequivocally support the military junta in Rangoon.”

“Thailand is simply out of step with the region and with other world democracies,” he said.

Myanmar has been under growing pressure in the region to make democratic reforms and release political prisoners, including Nobel Peace Prize laureate Aung San Suu Kyi. Some regional politicians have urged the junta to relinquish the chairmanship of the 10-nation Association of Southeast Asian Nations if it fails to do so.

McConnell said if Burma assumes the chairmanship, “the United States, the EU and the community of democracies should boycott any and all ASEAN meetings and events. To do anything less would betray the nonviolent struggle for freedom that Suu Kyi, the National League for Democracy (Suu Kyi’s party), and the ethnic minorities have waged for over a decade.”

The United States is not an ASEAN member, but regularly attends its sessions. The U.S. government has raised the possibility of boycotting ASEAN sessions if Myanmar assumes the chairmanship, but has not said it would do so.

Asked last week if the United States was urging ASEAN nations to get Myanmar to relinquish the chairmanship, a State Department official said that “ASEAN will decide what ASEAN thinks is best for the organization.” But the official added “It’s clear that Burma is a problem within that organization.”

“We’ve encouraged other countries, including other countries in ASEAN, to try to use whatever influence and ability they have to impress upon the leadership in Burma that they need to make changes,” the official said, speaking on condition of anonymity.

ASEAN members have been generally reluctant to criticize the Myanmar government’s human rights abuses because of a tradition of noninterference in each other’s domestic affairs. But criticism of Myanmar has been growing in Malaysia, Singapore and the Philippines.

On Wednesday, the United Nations’ envoy to Myanmar, Malaysian diplomat Razali Ismail, urged the region’s government’s to push harder for democratic reforms.