Washington, Feb 14 (DPA) Two astronauts conducted a spacewalk outside the International Space Station Sunday to outfit the orbiting laboratory's newest room, NASA said.

Nicholas Patrick and Bob Behnken, crew members of the visiting space shuttle Endeavour, connected outside cooling cables to the new Tranquility module. They also installed thermal covers on the Italian-made room and put in place handrails and other equipment to prepare for future spacewalks.

The astronauts spent five hours, 54 minutes working outside the ISS.

Meanwhile inside the station, Endeavour and ISS long-term crew members continued to prepare the inside of the new room.

NASA announced Saturday that the Endeavour's mission would be extended by one day to allow astronauts more time to move oxygen and water systems into Tranquility. Endeavour is now set to land at Kennedy Space Centre in Florida Feb 21.

The space agency also put off the depressurisation of Tranquility's glass six-windowed cupola after astronauts Saturday were unable to put a cover on the docking port where the cupola is currently located.

The cupola was taken into space attached to a temporary location on Tranquility to allow for easier transport. Astronauts are to move it to its permanent location where it will provide a panoramic view of earth later in Endeavour's mission.

But first they must install the cover to the docking port that currently holds the cupola. The cover is designed to provide protection from debris and temperature extremes when nothing is connected to the port.

Astronauts were to continue troubleshooting the cover Sunday in the hopes of going ahead with the cupola relocation which was originally scheduled for early Monday. NASA engineers back on earth were examining photos of the problem to aid the troubleshooting.

With the installation of Tranquility the space station is more than 90 percent complete. The US space shuttle, which is the only craft big enough to bring large components to the ISS, is to be retired later this year with just four more flight planned before September.

One more spacewalk is planned for Wednesday to outfit Tranquility.