WASHINGTON, Jan 19 (Reuters) - The U.S. Commerce Department said on Thursday it was launching an investigation that could lead to steep import duties on more than $100 million worth of wind energy towers from China and Vietnam.

The decision adds to the growing friction in clean energy trade between the world's two largest economies.

The department said it was also launching a separate probe into allegations of unfairly priced steel wire garment hangers from Vietnam and Taiwan. (Reporting By Doug Palmer; Editing by Doina Chiacu)