Despite being the No. 1 mobile phone manufacturer in the world, Nokia recently announced it expects to see lower net sales this quarter than previously anticipated.

In its second quarter 2011 outlook, the Finnish company said device and service sales will be "substantially below" the $8.7 billion to $9.5 billion range that it had originally expected. According to Nokia, this adjustment is due to an increasingly competitive market, lower selling prices of Nokia device and "pricing tactics."

However, the shift is also likely attributable to Nokia's recent decision to phase out its Symbian mobile operating system in favor of Microsoft's Windows Phone 7. Announced earlier this year, the partnership between the two companies will make WP7 the OS of choice on most Nokia devices.

No WP7-based Nokia devices have surfaced as of yet, but it does make sense that consumers would hold off on buying Symbian handsets, given that they will likely be obsolete in a few years. Nokia said it expects to ship its first WP7 handset in the fourth quarter of this year.

Last week, Microsoft launched the first major update to its mobile OS. According to reports, the update, dubbed Mango, is already run on several upcoming Nokia handsets.