The Grove-based team will instead take the wraps off the FW35 ahead of the second pre-season test at Barcelona's Circuit de Catalunya on February 19.
The team will run a 2012-spec FW34, sporting 2013 livery, for the four-day test at Jerez starting on February 5.
Williams are the first team to reveal their 2013 car will not be ready for the start of testing, with only Renault, Caterham and Marussia still to confirm their launch dates.
The nine-time constructors' champions finished eighth in the standings last year, despite Pastor Maldonado scoring a surprise victory at the Spanish Grand Prix.
Maldonado has been retained for the new season, but Bruno Senna has been released with Valtteri Bottas brought in as his replacement.