NEW YORK (AP) — Apple is delaying a big software update for the Apple Watch because it found a bug that is taking longer than expected to fix.

Apple Inc. said in a statement that it will not release watchOS 2, the new operating system for the Watch, on Wednesday as planned. It did not say when it will launch, only that it will happen "shortly."

The Cupertino, California, company has not said how many watches it has sold, though a recent report estimated it was about 3.6 million in the second quarter of this year. That's more than some analysts had forecast.

The public's response to the Apple Watch has been the subject of intense speculation. Critics have questioned whether it's useful enough for consumers to need or want one on their wrist.