An international project to build a nuclear fusion reactor in France that would start generating electricity in 17 years will face delays if U.S. cuts are not reversed in a few months, the head of the venture said on Tuesday.

Bernard Bigot, director-general of the International Thermonuclear Experimental Reactor project (ITER), said the Trump administration's budget cuts would reduce the U.S. contribution to the project and lead to construction delays.

"It's not a question of capability, it's a question of political will," Bigot said in a telephone interview while he was in Washington to meet with U.S. officials.