Formula 1 testing: Williams pull out of opening day in Barcelona
Williams have pulled out of the first day of pre-season testing on Monday as their new FW42 car is not ready.
Deputy team principal Claire Williams says the car will run on Tuesday - the second of four days of testing at Barcelona's Circuit de Catalunya.
Last week, the British team cancelled a planned shakedown run of the car because of delays in building it.
"It's clearly not ideal, but equally it's not the end of the world," Williams said.
"Our absolute priority is to always ensure we bring a car to the track that is the best that it can be and sometimes that takes longer than you'd anticipate or like."
Williams finished bottom of the constructors' championship in 2018 after picking up only seven points, with their drivers finishing in the top 10 in just two of the 21 races.
They have a new line-up this year with Robert Kubica returning to F1 after a nine-year absence alongside 21-year-old British Formula 2 champion George Russell.
"We have had an incredibly busy winter at Grove getting the FW42 prepared for the season ahead and, despite everyone's best efforts, we need some more time before it will be ready to run," Williams said.
"We will obviously have our work cut out to recover the time lost but we still have seven days of testing left and we will be maximising that time to prepare the car for the first race."
Next week is the first of two four-day pre-season tests, with the second on 26 February.
The new season begins on 15 March with the Australian Grand Prix in Melbourne.