The proposal must now be revised to take into account the negative comments made during the voting process.
Microsoft expects that a second vote early next year will result in approval, it said Tuesday. That is by no means certain, however, given the objections raised by some national standards bodies.
A proposal must pass two voting hurdles in order to be approved as an ISO standard: it must win the support of two-thirds of voting national standards bodies that participated in work on the proposal, known as P-members, and also of three-quarters of all voting members.
OOXML failed on both counts, ISO announced, as the working day ended in its Geneva offices.
The proposal won the support of 74 percent of voting members -- just shy of the required number. But only 53 percent of the voting P-members supported the proposal, well short of the required 67 percent.
Many of the national standard bodies voting against the OOXML proposal accompanied their votes with comments on what must be changed before they will vote in favor. ISO committee JTC1 must now reconcile those objections with the text, and find a compromise that will win enough votes to get through.
That will be difficult, as the French Association for Standardization, Afnor, wants to tear the proposal into two parts: a "core" part, which it wants to see converged over the course of three years with the competing Open Document Format (ODF), already an ISO standard, and an "extensions" part dealing with compatibility with legacy documents in proprietary formats.
France is not alone in suggesting modifications to the standard: Brazil raised more than 60 objections, including issues of support for different languages and date formats, while the standards body in India was concerned that OOXML is incompatible with the ODF standard.
Microsoft could miss out on revenue from the lucrative government market if OOXML is also rejected next year. Some governments, worried that the need for access to electronic archives held in proprietary formats leaves them hostage to their software vendor, have mandated the use of document formats that comply with open international standards.
Others are considering such a move, which could put Microsoft at a double disadvantage to open source products such as OpenOffice.org, which not only store files natively using Open Document Format, but are free.
"The OOXML format contains significant design flaws," and it will be difficult to correct them "other than by starting again from scratch, or by enriching the already existing standard, Open Document Format," he said Tuesday.
Industry body CompTIA said it was disappointed by the result, but echoed Microsoft's believe that the proposal will find enough supporters in the second round of voting. Microsoft is among the members of CompTIA, but OOXML opponents Sun Microsystems Inc. and IBM Corp. are not.
The ODF Alliance said while Microsoft has every right to seek the ISO label for its format, "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."
Office Open XML began as the default document format used by Microsoft's Office 2007 productivity suite. The company submitted the specification to ECMA International, an association of computer industry manufacturers, which modified it slightly and published it as the ECMA-376 standard before submitting it to ISO for fast-track approval as an international standard.