In an interview posted on Business Week, Microsoft's head of mobile development, Robbie Bach, stated:

Google started selling the Nexus One phone this week. The company also provides its Android operating system to other handset makers, rivaling Microsoft's Windows Mobile. Because Google now sells its own phone, handset makers may worry the company will prioritize its own product over theirs, Bach said. That could push some to stop using Google's software, he said.

“Doing both in the way they are trying to do both is actually very, very difficult,” he said in an interview yesterday from the Consumer Electronics Show in Las Vegas. “Google's announcement sends a signal where they're going to place their commitment. That will create some opportunities for us and we'll pursue them.”

Google's wireless efforts escalate the company's competition with Microsoft, a rivalry that spans Web search, browsers and business applications such as word processing and spreadsheets. The Android program is adding users faster than Windows Mobile, according to research firm iSuppli Corp.