After the February 11 announcement by Nokia, about its strategic alliance with Microsoft, Nokia’s CEO Stephen Elop made a surprise appearance during a presentation by Microsoft CEO Steve Ballmer at the Mobile World Congress (MWC); and elaborated what he terms as “a war of ecosystems.”

According to Elop, the Nokia-Microsoft partnership – which implies that Nokia will make Windows Phone 7 its primary mobile-phone platform, substituting its home-grown Symbian – will essentially create a new mobile ecosystem that will feature three key players: Apple, Google’s Android OS, and Nokia-Microsoft.

Elop expressed the opinion that Nokia’s new alliance with Microsoft will largely help the Finnish handset maker in gaining some of its ground in the smartphone market, as well as giving substantial challenge to Apple’s iPhone and Android-based handsets. Both Elop and Ballmer tried to convince the MWC attendees that they would be the “the most operator-friendly” choice.

However, despite the fact that Elop claims that Nokia will reap a profit of “billions” as a result of its partnership with Microsoft, the Nokia stock continued to slide, and analysts remained skeptical.

Noting that “the decision to transition its smartphone portfolio to Microsoft Windows Phone is a risky one for Nokia,” Alex Spektor, an analyst at Strategy Analytics Inc, said: “As Nokia transitions its smartphone portfolio to an entirely different platform, there is a risk that previously loyal Nokia consumers might abandon the vendor, hurting Nokia’s previously colossal smartphone volumes in the long term.”