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Nasa astronauts Christina Koch and Jessica Meir have made history by completing the first ever all-female spacewalk.

They spent seven hours outside the International Space Station (ISS) replacing a failed power control unit.

Ms Koch had already carried out four spacewalks but it was the first such mission for Dr Meir, who .

US President Donald Trump congratulated them in a video call. "You are very brave, brilliant women," he told them as they carried out the spacewalk.

Ms Koch, an electrical engineer, and Dr Meir, who has a doctorate in marine biology, stepped outside in their Nasa spacesuits at 11:38 GMT (07:38 EDT) on Friday. They made their way to a location called the Port 6 truss structure to replace the battery charge-discharge unit (BCDU).

They then returned to the airlock with the failed part which will subsequently be loaded on to the next SpaceX Dragon resupply ship for inspection on Earth.

Back on Earth, Democratic presidential candidate Kamala Harris tweeted that the spacewalk was "more than historic".

Nasa had announced in March that Ms Koch would take part in the first all-female "extra-vehicular activity" (EVA) with colleague Anne McClain. But the spacewalk was called off because a medium-sized suit wasn't available in the near-term for McClain.

The first woman to spacewalk was the Russian Svetlana Savitskaya, who went outside the USSR's Salyut 7 space station for three hours, 35 minutes on 25 July 1984.

The first person in history to spacewalk was Soviet cosmonaut Alexei Leonov, who died earlier this month aged 85.

On Tuesday, Nasa unveiled a prototype for a new spacesuit that might be worn by the next astronauts on the Moon. It said the new Moon suit, known formally as the Exploration Extravehicular Mobility Unit (xEMU), is designed to give the wearer a customised fit whatever their shape or size.