A US embassy worker, who was also the editor of Bangladesh's only LGBTI magazine was hacked to death on Monday in Dhaka.
A statement from the U.S. Embassy said Xulhaz Mannan was a "dear friend."
"We abhor this senseless act of violence and urge the Government of Bangladesh in the strongest terms to apprehend the criminals behind these murders," Marcia Stephens Bloom Bernicat, the U.S. ambassador to Bangladesh, said in the statement.
Mr Mannan and a friend were killed when five or six young men posing as couriers arrived at Mannan's building under the guise of delivering a package and hacked them to death with machetes.
US Secretary of State John Kerry also condemned the "barbaric murder".
"We offer our full support to the government of Bangladesh as they investigate these murders and bring the perpetrators to justice. We remain committed to the principles that were so important to Xulhaz, and we promise to support all those who work on behalf of tolerance and human rights in Bangladesh and around the world," Secretary Kerry said.