Microsoft announced Tuesday that it has sold more than 1.5 million Windows Phone 7 devices in the first six weeks.

"Sales are ramping well as our reputation is growing for offering users a unique experience and are in line with our expectations – especially when compared to other new platform introductions," Achim Berg, corporate vice president of mobile communications at Microsoft, said in a statement. "With a new platform you have to look at a couple of things, first of all customer satisfaction."

Microsoft has since sold 1.5 million devices, he said, though he did not break down U.S. versus international sales. "We know we have tough competition, and this is a completely new product. We're in the race – it's not a sprint but we are certainly gaining momentum and we're in it for the long run," he said.

Berg said Microsoft has "realistic" expectations for Windows Phone 7. "We started fresh with Windows Phone 7, and it's a different kind of phone. Measuring for success is more long term than short term," he said.

He pointed to the Windows Phone Marketplace, which now has 4,000 apps and 18,000 developers creating apps "We're comfortable with where we are, and we are here for the long run; Windows Phone 7 is just the beginning," Berg said.

Berg promised several Windows Phone 7 updates in the next couple months, as well as more mobile operators picking up Windows Phone 7 devices.

Microsoft unveiled its Windows Phone 7 lineup in October. Five devices from AT&T and T-Mobile are currently available in the U.S., with several more selling overseas. WP7 devices from Sprint and Verizon are expected next year. U.S. devices include the HTC Surround, LG Quantum, Samsung Focus, HTC HD7, and the Dell Venue Pro.