Microsoft's support for the OpenDocument Format (ODF) could mean greater opportunities for software makers already using the format, observers said Thursday.

Microsoft will put native support for ODF as part of its next service pack for Office 2007, due out by the first half of 2009. The surprise decision came as Microsoft's faces continued regulatory scrutiny from the European Commission over interoperability concerns.

The Commission said in a statement Thursday that it welcomes steps Microsoft takes toward "genuine" interoperability and that it would analyze the latest announcement to see how it impacts consumers' software choices.

In January, the Commission opened two new antitrust investigations against Microsoft concerning the interoperability of Windows with other software and the company's practice of bundling software products with Windows.

At least one office software maker thinks Microsoft's turnaround on ODF will mean more flexibility for software buyers. The ability to save in ODF in Microsoft Office could give users more confidence to switch to OpenOffice.org, a free open-source suite, said John McCreesh, spokesman for OpenOffice.org.

"The whole purpose of having an open standard is to give people freedom of choice," McCreesh said. "It means we have a level playing field, which is what it's all about."

Of course, those users could migrate to Microsoft from OpenOffice.org, too, McCreesh said.

A looming concern is if Microsoft's implementation of ODF within Office will handle documents with the same or better performance as competing suites. Microsoft has been criticized for embracing a particular standard but using subtle means within its software to subvert it.

Those concerns aside, one organization that has been particularly critical of Microsoft also welcomed the news. Wider user of ODF through Office could also give a boost to competing operating systems such as Linux, said the Free Software Foundation Europe.

"The move to support ODF, if genuine, would remove one of the most effective barriers for migration to GNU/Linux on the desktop," wrote Georg C.F. Greve, spokesman for the organization, in an e-mail. "The Microsoft desktop monopoly would be unlikely to continue in such a situation and millions of computer users would enjoy genuine freedom of choice."

Despite years of bitter criticism, Microsoft resisted putting native support for ODF in Office, instead supporting projects to create translators. Sun Microsystems developed one of those translators, which allows users to save in ODF in Microsoft Office 2003.

Microsoft also chose to push its Office Open XML (OOXML) format, which was approved by the International Organization for Standardization (ISO) in April. Opponents of OOXML said Microsoft's specification would unnecessarily splinter and complicate office software productivity products.

Microsoft said Wednesday that it would not implement ISO standard 29500, as the approved OOXML version is known, in Office 2007 but instead the next version of the program, known as Office 14.

That means ODF will have a few years' head start on the ISO's approved OOXML standard. Microsoft hasn't set a date for release of Office 14. Office 2007 was released first to business users in November 2006.