WASHINGTON (Reuters) - The U.S. Federal Aviation Administration on Wednesday said it would temporarily ground Boeing Co's 787s after a second incident involving battery failures caused one of the Dreamliner passenger jets to make an emergency landing in Japan.

The FAA said airlines would have to demonstrate that the lithium ion batteries involved were safe before they could resume flying Boeing's newest commercial airliner, but gave no details on when that could occur.

The agency said it would work with Boeing and the airlines to develop a corrective action plan that allowed the U.S. 787 fleet to resume operations as quickly and safely as possible.

(Reporting By Andrea Shalal-Esa)