Microsoft's move to add support for the Open Document Format to its Office suite has received a mixed reception.

The company revealed plans earlier this week to allow users to open, edit and save documents in ODF as well as Microsoft's competing Office Open XML (OOXML).

However, regulatory groups, Microsoft opponents and industry analysts are not convinced that the move will lead to harmony in the battle over control of the next-generation file format system.

The European Commission said in a statement that it will take a closer look at Microsoft's move.

"The Commission would welcome any step that Microsoft took towards genuine interoperability, more consumer choice and less vendor lock-in," said the Commission.

"In its ongoing antitrust investigation concerning interoperability with Microsoft Office, the Commission will investigate whether the announced support of ODF in Office leads to better interoperability and allows consumers to process and exchange documents with the software product of their choice."

ODF proponents were optimistic about the move. Jim Parkinson, vice president of developer tools and services at Sun Microsystems, welcomed the news.

"We look forward to working with Microsoft on the Oasis ODF Technical Committee to complete the improved ODF v1.2 specification and to submit it as an update to ISO/IEC," he said.

"This is valuable progress towards the interoperability and openness that customers are demanding worldwide."

Industry analysts suggested that, while the move is good news for the ODF camp, the war between the two formats is far from over.

"Microsoft's increased and improved support for ODF is real and it reinforces the idea that Redmond is moving to support open source, open standards and interoperability in response to customers, rather than contentions from critics or requirements from antitrust regulators," wrote 451 Group open source analyst Jay Lyman.

"Microsoft will certainly continue to work to support and promulgate OOXML and the format has a friend in the broad use of Microsoft's Office software.

"However, as OOXML faces continued scepticism, ISO appeals and an EU investigation, ODF stands ready for use with broad vendor support, growing adoption and, after this week, momentum."