NEW YORK, Jan 18 (Reuters) - The United States must focus on power reliability as it transitions away from fossil fuels to cleaner energy sources, Willie Phillips, acting chairman of the Federal Energy Regulatory Commission (FERC), said on Wednesday.

Electric power transmission, which FERC has identified as a top areas hindering the energy transition, will be key to stabilize the grid, said Phillips, who spoke at the District of Columbia Clean Energy Summit.

Phillips referred to widespread power outages suffered during winter Storm Elliott last month as one of the most recent examples of the vulnerabilities of a grid facing increased demand at the same time amid the shift towards renewable energy.

"It just reminds us that while we think about the clean energy transition and its importance, we have to continue refocus our efforts on reliability and resilience," Phillips said.

"One of the best ways that we can do this, both at the same time, is investment in transmission." (Reporting by Laila Kearney Editing by Chris Reese and Aurora Ellis)