"The United States strongly condemns ISIL's threat to murder Japanese citizens. We call for the immediate release of these civilians and all other hostages," Psaki said.
Psaki also announced that the United States is closely coordinating with Tokyo on resolving the hostage situation and stands "in solidarity with Japan."
US Secretary of State John Kerry will speak with Japanese Foreign Minister Fumio Kishida later on Tuesday to underscore American support, she added.
The ransom ties in with the $200 million that Japanese Prime Minister Shinzo Abe promised to provide to countries fighting against the IS during his journey to Middle East. Earlier today, Prime Minister Abe said that Japan was not going to give up the help it promised to fight the terrorist group.
The Islamic State is a jihadist group that has seized large territories in Iraq and Syria. The insurgents have kidnapped a significant number of people and last year released several videos, showing the executions of journalists and aid workers.