U.S. President Donald Trump on Friday signed orders meant to accelerate the construction of nuclear power plants, including small, untested designs that offer the promise of rapid deployment but haven’t yet been built in the U.S.

The effort is a bid to meet a coming surge in electricity demand and help the U.S. reclaim its edge in nuclear energy. While the country was once the leader in deploying and producing nuclear power, it’s finished building only two new reactors in the last 30 years and shuttered existing plants, even as China and Russia race to deploy them.

Trump’s initiative to unleash nuclear energy could give a boost to an emission-free source of power that’s championed as a climate-friendly alternative to electricity generated by burning coal and natural gas. However, the president has cast nuclear energy as a complement, rather than a replacement, for fossil fuels.