US Secretary of State Mike Pompeo said the United States was considering sanctions and other restrictions on those involved in the arrest of over 50 people in Hong Kong.
Pompeo also said in a statement that he was "appalled" by the arrest of an American citizen as part of Wednesday's crackdown and added: "The United States will not tolerate the arbitrary detention or harassment of US citizens."
Hong Kong police arrested 53 people in dawn raids on democracy activists on Wednesday in the biggest crackdown since China last year imposed a security law which opponents say is aimed at quashing dissent in the former British colony.
Among those detained was American lawyer John Clancey, a source at his firm said.
Pompeo called the arrests an "outrage and a reminder of the Chinese Communist Party's contempt for its own people and the rule of law."
"The United States will consider sanctions and other restrictions on any and all individuals and entities involved in executing this assault on the Hong Kong people," Pompeo said.
He said it would also "explore restrictions against the Hong Kong Economic and Trade Office in the United States, and take additional immediate actions against officials who have undermined Hong Kong's democratic processes."