Microsoft Corp Chief Executive Steve Ballmer said on Monday Windows Phone 8 being launched with its partners would create a strong third player in the smartphone market and sell quickly.

"With the work we have done with Nokia, HTC, Samsung and others ... there is now an opportunity to create really a strong third participant in the smartphone market," Ballmer said at an event to launch Microsoft's Windows 8 operating system in Israel, referring to Google's Android and Apple's iOS platforms.

Days after launching Windows 8, Microsoft is mounting a strong campaign to win over the software developers it needs to kick-start its new operating system.

A lack of apps is Microsoft's Achilles heel as it attempts to catch Apple Inc and Google Inc in the rush toward mobile computing.

Windows 8, the new Surface tablet and a range of Windows-based phones - all unveiled in the past week - are designed to close that gap, but the world's largest software company still needs to convince developers to recreate the thriving 'ecosystem' that made PCs so successful.

"There is a lot of work to do, the is a lot of work to do to get applications built and that means a lot of opportunity for people in the room today, there is a lot of work to do to really get a full set of devices in the market and get those to be broadly available, but the foundation is certainly there," Ballmer said.

Ballmer said Microsoft will do more marketing and advertising around Windows 8, its Surface tablet and Windows Phone than any products the company had ever done.

When Windows 8 launched, some major content providers had prominent apps in the Windows store, such as Netflix Inc , the New York Times and Rovio's Angry Birds Space. But big names such as Facebook and Twitter were missing.

Twitter moved to rectify that on Tuesday, announcing that a native Windows app would be rolled out "in the months ahead." Dropbox, a fast-growing cloud storage service, also announced it would soon have a Windows app, as did online payment firm PayPal and sports network ESPN .

But Facebook, which now has more than 1 billion users, has not yet made public any plans for a Windows app, despite the fact Microsoft is a minor shareholder.

And Microsoft still has to overcome indifference from many developers who do not see demand from users or simply do not have the resources to build Windows apps alongside iOS and Android.

To get more developers on board, Microsoft is spending this week demonstrating how it is making it easier to develop apps for Windows and get them into the real world.

"We're still relatively small ... I expect the volumes on Windows Phone to really ramp quickly," Ballmer said.

A key part of that is a new set of tools tying in its Azure cloud service, which allows Windows apps to easily harness data stored in remote servers.