McLaren's engineering director Paddy Lowe says the team had always intended to wait until after the first 2011 test before launching its new car, and is not behind schedule.
The McLaren-Mercedes MP4-26 will not be revealed until a Berlin event on 4 February, the day after the first winter test at Valencia ends.
While all the other frontrunners - including Red Bull, which has launched late in recent years - will run 2011 machines at Valencia, Lowe said McLaren preferred to get a benchmark with the new Pirelli tyres on its 2010 car first.
"It's always been in our plans to launch it after the first test," he said during a Vodafone McLaren Mercedes phone-in.
"One of the reasons was that we wanted to make use of the first test to work with the new car as a stable and known platform while we understood the new tyres. It also gave us a bit more time in the programme for the new car.
"So it's always been planned that way. It's just a plan we arrived at and one we considered optimal in race preparation overall."
Lowe revealed that the car used at Valencia would be largely a 2010 model rather than an interim machine.
"It's a relatively standard 2010 chassis," he said. "We have a number of development items on it, but nothing substantial in terms of elements of the 2011 package."
He acknowledged that McLaren was taking a risk by opting for a different testing strategy to all its main rivals.
"It's always a bit of a balancing act between how much mileage you're going to cover from the reliability point of view and a set-up point of view working with the new car," said Lowe.
"Then you're trading against development time in the lab and the windtunnel and in the office.
"In terms of reliability impact, more and more work is now done in the lab, typically on the dynamometer, to prove out the major mechanical systems on the car. So we're more confident these days that we can hit the ground running with a reliable package without needing to do thousands and thousands of kilometres on the track.
"You always do learn something from the mileage, but it's a trade. I hope we're not proven wrong in that respect, but we're reasonably confident that we can get the reliability that we need from those three tests."
Renault team boss Eric Boullier speculated that McLaren's late launch might be because the squad was perfecting a surprise innovation such as the F-duct, which it pioneered last winter.
"You never know the reasons behind it. It is obviously a strange decision, it could be a strategic decision as well," Boullier told AUTOSPORT.
"They have maybe tried to bring some very funny new systems, like they did, last year and they maybe need more time to manufacture them."