Apple sends out invites for its March 21 spring event

Apple will hold its spring product launch on March 21, one day before it squares off with federal prosecutors over the government's demand for help unlocking an encrypted iPhone.

Analysts and tech blogs are expecting Apple will announce a new, 4-inch iPhone, a smaller iPad Pro and new bands for the Apple Watch. But the company provided no details with its announcement of the event, in keeping with its usual effort to build anticipation for its new products.

An invitation sent to reporters on Thursday said only "Let us loop you in." Apple's headquarters is located on a road called Infinite Loop in Cupertino, California. Apple's twice-yearly product events are highly anticipated and the speculation that precedes them is rampant. The backdrop to this year's event is a high-stakes legal dispute with the FBI and the Obama administration, which has chafed at Apple's use of encryption that make its customers' data unreadable to others.

Federal authorities want Apple's help in over-riding security features on an iPhone used by one of the San Bernardino mass shooters, so the FBI can attempt to examine the phone. Apple CEO Tim Cook contends the government's demand would make other iPhones vulnerable. Both sides will make their case to a federal magistrate in Riverside on March 22. While Apple executives say the company is continually working on increased security measures, they haven't said whether they will announce any new encryption or other safeguards at this month's event.