SAN FRANCISCO — Google Inc. will introduce a spreadsheet program today, continuing the Internet search leader's expansion into territory long dominated by Microsoft Corp.

Although it's still considered a work in progress, Google's online spreadsheet will offer consumers and businesses a free alternative to Microsoft's Excel application — a product typically sold as part of the Office software suite that has been a steady moneymaker for years.

To avoid swamping the company's computers, Google's spreadsheet initially will be distributed to a limited audience. Google also wants more time to smooth out any possible kinks and develop more features, said Jonathan Rochelle, the product manager of the new application.

The Mountain View, Calif.-based company planned to begin accepting sign-ups for the spreadsheet at 3 a.m. Hawai'i time today through the "labs" section of its Web site.

Rochelle wouldn't specify how many people will be granted access to the spreadsheet application.

Google's spreadsheet isn't as sophisticated as Excel. For instance, the Google spreadsheet won't create charts or provide a menu of controls that can be summoned by clicking on a computer mouse's right-hand button.

Rochelle said the program's main goal is to make it easier for family, friends or co-workers to gain access to the same spreadsheet from different computers at different times, enabling a group of authorized users to add and edit data without having to e-mail attachments back and forth.

"We are totally focused on the sharing aspect," he said.

Although distributing software over the Internet gives more people greater access to programs, the approach requires trusting a custodian like Google to save and protect the information from unauthorized users.

That's a leap many security-conscious companies are unwilling to make and something consumers may be reluctant to do amid rising concerns over government snooping.

The spreadsheet represents Google's latest software application to be tethered to an Internet connection instead of a single computer's hard drive. Google acquired an online word processing application called Writely in March and rolled out a calendar service a few weeks later.

All of those free programs pose a possible threat to Microsoft, which established itself as the world's largest software maker by selling its Windows operating system and complementary applications that run on the platform.

As Google invades its turf, Microsoft has been mounting its own attack by investing heavily in Internet searching.

Microsoft's assault hasn't hurt Google yet, but some industry analysts believe the competitive landscape could shift early next year with the release of Vista — the long-delayed upgrade to the Windows operating system.