Nokia has declared war in the US smartphone market, with a Microsoft-powered handset tailored to take on Apple iPhones and Google-backed Android devices.

Microsoft chief executive Steven Ballmer joined Nokia boss Stephen Elop on Monday to unveil the new Lumia 900 smartphone, which will run on Windows mobile software and tap into a growing trove of popular mini-applications.

The two firms did not disclose the price or release date for the Lumia 900, but said it will be offered exclusively on the latest generation 4G LTE network of US telecom giant AT&T.

"We believe the industry has shifted from a battle of devices to a war of ecosystems," Elop said, in a presentation laden with martial metaphors.

"Clearly there are strong contenders on the field in this war of ecosystems," he told a room packed with press on the eve of the opening of the annual Consumer Electronics Show (CES), a massive gadgets fair in Las Vegas.

The Finland-based Nokia in October introduced the Lumia line, which Elop described as the "first real Windows phones," which had established "beachheads" in Europe, India, and Hong Kong.

The company planned to start the US invasion on January 11 with a Lumia 710 model that will be priced at $49 when bought with T-Mobile service contracts.

"The work Nokia is doing around Windows phone and this third ecosystem is really going to pay off," Ballmer said, caressing a sleek Lumia 900 touchscreen handset.

"When you pick it up and love and touch and feel your Lumia," he said -- making a playful "mmmmm" sound that drew laughs -- "it really is quite fantastic."

Ballmer praised Nokia for getting the phones to market less than a year after striking a deal with Microsoft to use its mobile software and link to its online applications shop, which boasts a fast-growing bank of 50,000 apps.

"The reviews have been fantastic," Ballmer said of Windows-powered phones, which have been late-comers to a booming market increasingly dominated by Apple and Android handsets.

Lumia 900 has front and rear facing cameras with Carl Zeiss photo technology and 4.3-inch high-definition displays.

"I think Nokia is going to be back in the US in a very big way," AT&T president of mobility Ralph de la Vega said at a press conference.

"We are big fans of Windows phones."

Nokia showed off an array of applications made just for Lumia 900, including 20 videogames made by console industry colossus Electronic Arts.

Elop said Nokia planned to price Lumia 900 "aggressively" to establish a strong beachhead on the US smartphone battlefield. He said that Lumia would then land in China and Latin America to fight for market share.

"I am so happy that companies like Samsung, HTC and others are all introducing Windows devices," Elop said. "We all need to get that fly wheel spinning; our principle competition is the other ecosystems."

Nokia plans to eventually extend Windows across its full range of mobile phones and was working with Microsoft on getting mobile gadgets and computers to share pictures and other content using the Internet "cloud."

While declining to comment specifically on Research In Motion (RIM), Elop said that Nokia sees opportunity to compete in the business smartphone market, which has long been a stronghold for RIM's popular BlackBerry handset.