Miami (AFP) - An American astronaut found water pooling inside his helmet after he finished a six-plus hour spacewalk on Wednesday, raising new concerns about the safety of NASA's spacesuits.

Terry Virts was not harmed during the incident, which the US space agency described as "minor" compared to the near-drowning of an Italian astronaut when a similar problem occurred in 2013.

But mission managers will be poring over the data at a meeting on Friday to decide whether another spacewalk can go ahead as planned on Sunday, a NASA spokesman said.

Even before this series of three spacewalks began on Saturday, NASA voiced concern about a recurring problem with the American spacesuits in a part of the temperature control system known as the fan pump separator.

Virts did not notice any water during the spacewalk, as he toiled for hours to lubricate the latching mechanisms on a robotic arm and helped his colleague Barry Wilmore get the space station's exterior ready for the arrival of commercial spaceships carrying astronauts in the coming years.

Their spacewalk lasted six hours and 43 minutes.

It was only after Virts was done, and had re-entered the Quest airlock, that he began to feel dampness on the back of his head and saw water pooling near the front of his headpiece.

The water inside Virts' helmet was "kind of pooling on the front side of his helmet above the eye level," European Space Agency astronaut Samantha Cristoforetti told mission control in Houston.

The water was "about three inches in diameter," she said, noting that the amount of water had increased in the moments since he first noticed it.

NASA television showed live images of Virts smiling inside his helmet and blowing on the water to make it ripple, before eventually removing the headpiece with Cristoforetti's help.

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