Microsoft's campaign to standardise its Office OpenXML file format took a hit today when a US committee voted against approving the format and supporting it for approval by the International Organization for Standardization (ISO).

The motion required approval from nine of the 16 voting organisations comprising the International Committee for IT Standards. Eight voted in favour of approving OpenXML, while seven voted against.

The Institute of Electronics and Electrical Engineers abstained from the vote, claiming that its members could not reach a consensus.

Members voting in favour of approving OpenXML for standardisation included Apple, Intel and HP.

Among those voting 'no' were Lexmark, Oracle and IBM, which backs the rival ODF file format.

The ODF and OpenXML camps have been engaged in a bitter fight over standardisation. ODF was approved last year by the ISO.

The approval is important because it plays a key role in winning over the various government bodies that are currently seeking to adopt a single file system for all official documents.

Two major US government offices fell on opposite sides of the debate. The Department of Homeland Security (DHS) voted in favour of approval, while the Department of Defense (DoD) voted against.

"Despite the international controversy between ODF and Office OpenXML, the DHS sees reason for both of these standards to coexist as approved ISO specifications," said the DHS.

"The document data models are each peculiar to the legacy formats and carry different strengths and weaknesses in their specifications."

The DoD disagreed, saying that OpenXML had security and compatibility concerns. "The DoD position is based on the requirement to resolve existing comments and further develop/mature the present state of the standard," said the department.