U.S. Defense Secretary Ash Carter (L) and Chairman of the Joint Chiefs of Staff Joseph Dunford testify before a Senate Armed Services Committee hearing on National Security Challenges and Ongoing Military Operations on Capitol Hill in Washington, U.S., September 22, 2016. REUTERS/Yuri Gripas

U.S. Defense Secretary Ash Carter testifies before a Senate Armed Services Committee hearing on National Security Challenges and Ongoing Military Operations on Capitol Hill in Washington, U.S., September 22, 2016. REUTERS/Yuri Gripas

U.S. Defense Secretary Ash Carter testifies before a Senate Armed Services Committee hearing on National Security Challenges and Ongoing Military Operations on Capitol Hill in Washington, U.S., September 22, 2016. REUTERS/Yuri Gripas

U.S. Defense Secretary Ash Carter shakes hands with Sen. Kelly Ayotte (R-NH) before a Senate Armed Services Committee hearing on National Security Challenges and Ongoing Military Operations on Capitol Hill in Washington, U.S., September 22, 2016. REUTERS/Yuri Gripas

People talk outside the headquarters of the World Trade Organization (WTO) in Geneva, Switzerland, June 3, 2016. REUTERS/Denis Balibouse

U.S. Trade Representative Michael Froman speaks to reporters after a meeting with Japan's Economics Minister Akira Amari in Tokyo April 19, 2015. J REUTERS/Yuya Shino

An Airbus logo is pictured on the company booth during the European Business Aviation Convention & Exhibition (EBACE) at Cointrin airport in Geneva, Switzerland, May 24, 2016. REUTERS/Denis Balibouse

The logo of Lufthansa airlines is seen at a closed counter of the company, at the Simon Bolivar airport in Caracas, Venezuela May 30, 2016. REUTERS/Carlos Garcia Rawlins