"Microsoft is committed to interoperability, transparency and user choice," he said. "That is why we are supporting additional formats going forward; after all, users have always wanted access to multiple formats, and now they have even more options."

Microsoft has agreed to support ODF in Office as part of Office 2007 Service Pack 2, which is due out between February and April 2009, and eventually it will implement the current OOXML specification in Office 2007 as well.

Last week, Microsoft publicly outlined how it would implement ODF in that service pack release and expects to in the next several weeks to release implementation notes for ECMA 376 as well.

However, Marcich expressed concern over the implementation of ODF revealed by Microsoft last week, saying it has raised some eyebrows among ODF proponents for not being in line with how the ODF specification is currently implemented.

"It suggests that Microsoft will deviate substantially from the course taken by other vendors," he said. "This could break interoperability."

ODF proponents have reason to worry, as the process to ISO approval for OOXML was riddled with complaints that Microsoft acted unscrupulously, the standards process was not implemented properly and the specification approved was too unwieldy to implement.

Mahugh, however, defended Microsoft's planned implementation of ODF, saying the company is "confident" in it, which is why Microsoft "took the step of publicly disclosing the principles and priorities that guided our development, released our implementation notes, and are supporting DII events around the world," he said. DII, or the Document Interoperability Initiative, is a group Microsoft created to foster interoperability between different document formats .

Mahugh added that Microsoft encourages other ODF implementers to "provide a similar level of transparency and participate positively" in the company's DII events.