Myanmar’s global political woes have become a thorn in the side of a major foreign investor.

A bid by Japanese conglomerate Kirin International Holdings to buy an American beer brand has come under fire thanks to Kirin’s stake in Myanmar Brewery, which it shares with the Myanmar-backed Myanmar Economic Holdings Limited. Kirin plans to acquire New Belgium, a notable American beer maker. But an open letter by two ethnic Karen refugee organizations has called for New Belgium employees to speak out against the deal.

“Most of us sought protection in the USA to escape from the Burmese army’s campaigns of ethnic cleansing that targeted Karen and other ethnic minorities,” says the letter, which was submitted by the Karen Community of North Carolina, the Karen Organization of America and Inclusive Development International. “The Burmese state and its key actors have committed genocide against the Rohingya people of Burma, and crimes against humanity against other ethnic minorities, including the Karen.”

The collapse of a major deal for Kirin would be the first significant victory for the global boycott against army-linked businesses, recommended by the UN in August. For now, however, New Belgium plans to move forward with the deal. In a statement sent to The Colorodan, a publication in the state of Colorado, where New Belgium is based, the beer maker said that while the letter “gave [New Belgium] pause, we believe Kirin’s commitment to human rights aligns with our mission and we remain fully committed to our core values and beliefs.”