Microsoft is continuing to gradually expand its distribution channel for its Surface tablets.

Microsoft will expand its current list of a "couple hundred" authorized Surface device distributors to a few thousand worldwide, said Gavriella Schuster, General Manager of Microsoft's Worldwide Partner Program.Microsoft is announcing its channel-expansion plans on July 13, the first day of its annual Worldwide Partner Conference in Orlando.

Any partner can sign up for the expanded Surface distribution program, though each distributor will have qualifications based on volume.

"We expect to get a few thousand resellers to jump on this," Schuster said.Microsoft is broadening its distribution channel for Surfaces ahead of the start of its Windows 10 launch.

Microsoft's existing line of Intel-based Surfaces -- the Surface Pro, Surface Pro 2, Surface Pro 3 and Surface 3 -- will all be upgradable to Windows 10. Microsoft officials have said the ARM-based Surfaces -- Surface RT and Surface 2 -- will not be upgradable to Windows 10. Instead, Microsoft will offer users with ARM-based Windows devices some kind of an update for their machines which will include a subset of Windows 10's features.

Microsoft officials still aren't saying exactly when the company will deliver the update for ARM-based Windows machines or which features it will include.

As of last fall, Microsoft had authorized only 20 distributors and resellers to carry its Surface tablets under Microsoft's Authorized Device Reseller program.

Microsoft launched its Authorized Device Reseller Program for Surface in July 2013. At that time, company officials said it would be a two-tier program, which authorized three distributors to sell Surfaces to a handful of authorized commercial resellers, who, in turn, could sell these devices to business customers.