NASA astronaut Terry Virts Flight Engineer of Expedition 42 is seen working to complete a cable routing task while the sun begins to peak over the Earth's horizon on the International Space Station, in this handout photo taken February 21, 2015, provided by NASA. Virts and fellow astronaut Barry "Butch" Wilmore completed a 6-hour, 41-minute spacewalk routing more than 300 feet of cable as part of a reconfiguration of the station to enable US commercial crew vehicles under development to dock to the space station in the coming years. [Photo/Agencies]

WASHINGTON - A pair of US astronauts ventured outside the International Space Station on Wednesday for the second of three spacewalks to prepare the orbiting lab for future American crew spacecraft.

The nearly seven-hour spacewalk by astronauts Barry Wilmore and Terry Virts went smoothly with all the scheduled tasks completed, but back inside the station's airlock, Virts reported a small amount of water floating free in his helmet.

There was no report of water during the spacewalk itself and the crew was never in any danger, NASA said in a statement.

During their first spacewalk on Saturday, the two astronauts spent six hours and 41 minutes outside deploying eight bundles of cables. Wednesday's spacewalk featured more cable work.

Wilmore and Virts "completed rigging a series of power cables on Pressurized Mating Adapter-2, lubricated the Latching End Effecter of the space station's Canadarm2 robotic arm, and prepared the Tranquility module for the station's upcoming reconfiguration in preparation for the arrival of commercial crew vehicles later this decade," the US space agency said.

"They also were able to complete get-ahead work for the installation during Sunday's spacewalk of the Common Communications for Visiting Vehicles system by pre-staging wire- ties that will be used to secure some 400 feet (122 meters) of cable," it added.

Wednesday's spacewalk began at 6:51 am EDT (GMT1151) and ended at 1:34 pm (1834 GMT) with the repressurization of the station's Quest airlock, and it was at that time that Virts noticed the water problem.

The water was "about three inches (seven centimeters) in diameter" and "it's kind of pooling on the front side of the helmet above his eye level" said European Space Agency astronaut Samantha Cristoforetti who helped remove Virts' helmet.

Cristoforetti also told flight controllers in Houston that the helmet absorption pad was damp, but not saturated, indicating that the water may not appear until very late in the spacewalk.

NASA said ground teams are currently analyzing the situation to confirm the source of the water.

The spacewalk was the third for Wilmore and the second for Virts. The duo was originally scheduled to perform a third spacewalk on Sunday. But given the water problem, NASA said will meet on Friday to review the issue.

In 2013, NASA aborted a planned six-hour spacewalk after Luca Parmitano of the European Space Agency reported a buildup of water inside his helmet.