Spacewalking astronauts routed more than 300 feet of cable outside the International Space Station on Saturday, tricky and tiring advance work for the arrival of new American-made crew capsules.

It was the first of three spacewalks planned for NASA astronauts Butch Wilmore and Terry Virts over the coming week.

Altogether, Wilmore and Virts have 764 feet of cable to run outside the space station. They got off to a strong start Saturday, rigging eight power and data lines, or about 340 feet.

"Broadening my resume," Virts observed.

NASA considers this the most complicated cable-routing job in the 16-year history of the space station. Equally difficult will be running cable on the inside of the complex.

The extensive rewiring is needed to prepare for NASA's next phase 260 miles up: the 2017 arrival of the first commercial spacecraft capable of transporting astronauts to the orbiting lab.

NASA is paying Boeing and SpaceX to build the capsules and fly them from Cape Canaveral, which hasn't seen a manned launch since the shuttles retired in 2011. Instead, Russia is doing all the taxi work -- for a steep price.

The first of two docking ports for the Boeing and SpaceX vessels -- still under development -- is due to arrive in June. Even more spacewalks will be needed to set everything up.

There were so many cables that NASA color-coded them. That helped the spacewalkers only so much; they expected a lighter blue for one of the lines.

"I worked up a lather on that one," Wilmore informed Mission Control. After successfully attaching the first four cables, he added, "I've got to cool down."

Mission Control left two cables -- or about 24 feet worth -- for the next spacewalk coming up Wednesday. Four hundred feet of additional cable will be installed March 1 on spacewalk No. 3.

"We've got a lot of work still," Mission Control said as Saturday's 6 1/2-hour spacewalk drew to a close. "We want to make sure we look after your health and get you back inside now, so we're going to claim victory here."

It was the first spacewalk for Virts, who arrived at the space station in late November. He savored the moment as he floated out high above the South Pacific. "Pretty cool," he said.

Spacesuit concerns stalled the work by a day.

NASA wanted to make certain that the suits worn by Wilmore and Virts had reliable fan and pump assemblies. Two other fan-pump units failed aboard the space station in recent months and were returned to Earth earlier this month for analysis. Corrosion was discovered, the result of water intrusion from testing.

Their suits appeared to work fine Saturday.

"I just wanted to say thanks to everyone for their hard work and diligence," Wilmore, the station's commander, said once he was safely back inside.