Microsoft Corp. said it plans to expand the capabilities of phones running its Windows Phone 7 software later this year, as it tries to catch up with the Apple Inc. and Google Inc. in the mobile market.

Speaking at the Mobile World Congress in Barcelona, Microsoft Chief Executive Steve Ballmer unveiled the updates for the company's smartphone software, including integration with Twitter and the ability to run multiple applications simultaneously, a feature already present in many competing devices.

The advancements come as Microsoft attempts to increase its influence in the fiercely competitive U.S. smartphone market led by devices running Google's Android software and the Apple iPhone.

Microsoft's plans also follow last week's unveiling of a partnership between the Redmond, Wash.-based software giant and Finnish phone giant Nokia Corp. that would put Windows Phone 7 software on Nokia devices later this year. Both companies said they expect to benefit greatly from the partnership, giving Microsoft access to many more customers while injecting new life into Nokia's smartphone business.

Microsoft, which released its Windows Phone 7 software last year, is seen as a laggard in the market, missing key technologies and lacking interest among mobile-application developers, all key to success in the new and quickly growing market.