Two U.S. astronauts were venturing outside the International Space Station (ISS) Wednesday to replace a failed power regulator, U.S. space agency NASA said.

NASA astronauts Reid Wiseman and Barry Wilmore began the spacewalk at 8:16 a.m. EDT (1216 GMT), the agency said in a statement.

The two will also relocate equipment on the station's exterior to begin setting the stage for a reconfiguration of the orbiting complex to accommodate future commercial crew vehicles, it said.

It is the second spacewalk for Wiseman and the first for Wilmore.