Google Inc. has signed a deal to provide email and online-collaboration software to more than 100,000 employees at General Motors Corp. , according to people familiar with the matter.

The contract, however, requires Google to meet certain requirements before GM makes a final decision to deploy the software, these people added.

A GM spokeswoman declined to comment on the Google contract but said the company has "not made a decision to deploy Google Apps. We're always looking for leading-edge technologies, and our [information technology] department is open to various developers."

Assuming Google wins final approval, the deal could be a watershed moment in Google's quest to challenge Microsoft Corp.'s dominance in application software, marking the largest deal since the Internet company began selling what it calls Google Apps in 2007.

Google Apps includes Gmail and Google Docs, which competes with Office applications such as Word, Excel and PowerPoint. It now also includes the Google+ social networking service, which features video conferencing.