Check out the schedule below:
- Jennifer Williams, an aide to Vice President Mike Pence
- Tim Morrison, the top Russia and Europe adviser on the National Security Council
- US Ambassador to the European Union Gordon Sondland (previous testimony transcript)
- Laura Cooper, a deputy assistant secretary of defense for Russia, Ukraine and Eurasia (previous testimony transcript)
- David Hale, the under secretary of state for political affairs
This story has been updated with additional developments Monday.