Microsoft has lost a preliminary vote to have its Office Open XML document format approved as an international standard, denting the company's hopes of wider adoption of the standard by public-sector organizations.

The result of the International Organisation for Standardisation (ISO) ballot, announced on Tuesday, was hailed as a victory for open standards by supporters of the rival Open Document Format, who argued the Microsoft format was not open, but a ploy to lock in users.

Microsoft failed to capture a two-thirds majority in the vote to approve the file format as a global standard, but the group will meet in February to hammer out a consensus, allowing the world's largest software maker more time to grab votes.

Microsoft's Office Open XML (OOXML) is the default file-saving format in Microsoft Office 2007, the latest version of its dominant productivity software. The Open Document Format (ODF) has already garnered international standard status from the ISO.

Microsoft argues that its format has higher specifications and is more useful than ODF, while opponents say Open XML's 6,000 pages of code compared with ODF's 860 pages make it complicated and untranslatable into other formats.

Free and rival productivity software suite OpenOffice.org uses ODF, an open standard supported by IBM and Sun Microsystems.

The standardization of Open XML would allow other companies to build products using the file format and simplify file exchange between different software suites.

The ISO said in a statement on Tuesday that 53 percent of the votes cast by national standards bodies were in favor of Microsoft, missing the necessary two-thirds majority.

Twenty-six percent of national votes cast were against approving Open XML in the five-month ballot process, in which 104 national member bodies were entitled to vote.

The ODF Alliance said in a statement that the large number of "no" votes "demonstrates the depth of concern around the world over OOXML's interoperability and openness."

"Microsoft has every right to seek the ISO label for OOXML, but, as the ballot results show, it has a long way to go before it earns it and can be considered a truly open, interoperable document format," it said.