The previously announced date was March 12, following five delays caused by concerns over the safety of three valves that control the pressure in the shuttle's fuel tanks. NASA said its experts had replaced Discovery's valves with spares that should be less susceptible to cracking.
NASA officials are planning to hold a formal review of the valves' safety on March 6 to set an official date for the Discovery launch.
The Discovery's 7-man crew includes Japan's Koichi Wakata, who will replace returning ISS engineer Sandra Magnus.
Eight more flights to the station remain before the space shuttle is put into retirement in 2010 and all transport flights to the ISS switch over to Russian Soyuz and Progress spacecraft at least until 2013.
During the upcoming 14-day mission, Discovery will deliver the last set of solar wing panels to the ISS to increase power generation at the station, which will soon accommodate six astronauts instead of the current three.
