BERLIN (Reuters) - German Chancellor Angela Merkel and French President Francois Hollande underscored the need for European unity in the face of growing internal and external threats, including the rise of populism across Europe and U.S. threats to abandon free trade.

"Europe faces big internal and external challenges which we ... can only master by working together," Merkel told a news conference on Friday with Hollande.

She added: "We need a clear, common commitment to the European Union, to what we have accomplished, and to the values of our liberal, democratic democracies."

Hollande said the rise of populists on the continent was a major threat for the European Union.

"To be very honest, what threatens Europe doesn't only come from outside. It is also from inside. This means the rise of extremists who use external factors to cause disruption internally," Hollande said.

The two leaders did not take questions.

(Reporting by Andrea Shalal and Joseph Nasr; Editing by Michael Nienaber)