The European Space Agency said earlier that Hans Schlegel had recovered from the unidentified ailment, while NASA said the space walk was on schedule for Monday, Schlegel nevertheless was pulled off the walk, which is to begin hooking up the European Columbus science research module delivered to the ISS aboard the US Atlantis space shuttle. He will be replaced by US astronaut Stanley Love, who will join Rex Walheim on the exercise

Schlegel, one of seven astronauts, including two Europeans, who rode the Atlantis up to the ISS, was reported ill just after the shuttle docked Saturday at the space station, two days into the mission, but early Sunday Markus Bauer, the spokesman for the European Space Agency, said Schlegel, 56, appears to have recuperated and was doing "very well", "We are assuming that he will take part in the second spacewalk," said Bauer.

NASA refused to give details on his sickness, citing respect for the astronaut's private life, While Schlegel's ailment remains unexplained; the German astronaut -- who joined a shuttle mission in 1993 -- spoke to Mission Control in Houston after waking up shortly before 1000 GMT Sunday.

The delay to the first spacewalk has forced the National Aeronautics and Space Administration to extend the original 11-day mission of the shuttle Atlantis by one day, setting its return to Earth on February 19.

The Atlantis mission to deliver the 10-tonne Columbus laboratory marks a milestone in Europe's role in space. Paid for mostly by Germany, Italy and  France, it is the first ISS addition not made  in the United States or Russia, The laboratory will be used for biotechnology and medicine experiments involving microgravity.