WASHINGTON, Feb. 21 -- A pair of U.S. astronauts successfully completed the first of three spacewalks on Saturday, installing over 100 meters of cable outside the International Space Station as part of a preparation for future arrivals of American commercial crew spacecraft.

NASA astronauts Barry Wilmore and Terry Virts "completed all the scheduled tasks for today and one get ahead task," the U.S. space agency said in a statement. "They rigged a series of power and data cables at the forward end of the Harmony module and Pressurized Mating Adapter-2 and routed 340 of 360 feet (110 meters) of cable."

The cable routing work is part of a reconfiguration of station systems and modules for the installation of two international docking adapters to be delivered by a pair of SpaceX Dragon cargo spacecraft later this year.

The new docking ports will welcome U.S. commercial spacecraft launching from Florida beginning in 2017, permitting the standard station crew size to grow from six to seven and potentially double the amount of crew time devoted to research from 40 hours to 80 hours per week, NASA said.

The two astronauts ventured out of the station at 7:45 a.m. EDT (1245 GMT) and reentered the orbiting outpost at 2:26 p.m. EST ( 1926 GMT).

The spacewalk was the first for Virts, and the second for Wilmore, who has conducted one spacewalk last October.

The duo will perform two more spacewalks on Wednesday and March 1.

Because the spacewalks focused on laying and attaching cables, NASA's space station blog called the two astronauts "cable guys."

NASA has relied on Russia's Soyuz capsules to deliver astronauts to the station since the end of the space shuttle program in 2011.

In order to end the reliance, the U.S. space agency awarded contracts last year to Boeing and SpaceX to develop solutions for American astronaut transportation to and from the station.

Currently, Boeing is working with NASA on its CST-100 spacecraft, anticipating an orbital flight test in April 2017, then a crewed flight test with one Boeing test pilot and one NASA astronaut in July 2017.

SpaceX is targeting its new crewed Dragon spacecraft to make an uncrewed flight test in late 2016 and a crewed flight test in early 2017.