Microsoft will roll out its latest phone operating system, currently codenamed Mango, to Windows Phone 7 users starting on 1 September, Pocket-lint has exclusively learnt. Therefore, that will be the date that the company will start its fightback against Android and the iPhone. 

Multiple trusted sources have confirmed to us that the start of next month will see the new OS, available to developers over the summer, launching on new handsets, as well as becoming available to current WP7 customers. 

Previously, Microsoft has opted simply to say "Fall" when asked about its date of availability.

The launch date, we now understand, has been chosen due to its importance in tieing in with IFA, Europe's largest consumer electronics show in Berlin, and means that companies like Samsung, Acer, ZTE and LG will be able to show off new devices with Mango installed.

Additionally, Nokia is expected to launch its Windows Phone 7 offering at Nokia World at the end of October, giving Microsoft a double whammy in the run up to Christmas. 

Microsoft first announced Mango, the second version of its mobile phone software at MWC in Barcelona in February. And Pocket-lint checked out a later build as a first look review at the end of June.

Microsoft has so far declined to comment.

Could this make WP7 a valid rival to Android and iOS? Let us know your thoughts in the comments below...