NEW YORK (

TheStreet

) -- In a market where apps help make the smartphone, mobile developers are holding off on building applications for

Microsoft's

(MSFT) - Get Report

Windows Phone 7 platform until they see that it will sell.

Windows Phone 7, which hit stores last week, is playing catch-up in the competitive, booming smartphone race led largely by

Apple

(AAPL) - Get Report

and

Google's

(GOOG) - Get Report

Android platform.

>>Apple iOS 4 vs. Android: Developer Wars

"Developers are having a wait-and-see attitude to see how Windows performs," said Patrick Mork, chief marketing officer at

GetJar

, an independent mobile app store. "There's just a big question mark."

Despite the fact that developers say they are impressed with Windows Phone 7 and praise the ease of writing for the platform, they're concerned about the market opportunity. Large, well-funded companies like

Facebook

and

Electronic Arts

(ERTS)

are willing and able to create applications for Windows Phone 7, but smaller outfits with limited resources may be hesitant to invest time and capital in a smartphone whose success is not yet validated, said Mork.

Microsoft reportedly sold only

40,000 Windows Phone 7 devices

on launch day, which pales in comparison to the number of phones sold per day by Apple (270,000) and with Google's Android (200,000).

Moving forward, research shop Gartner predicts that Windows Phone 7 will claim just 3.9% of the worldwide mobile operating system market by 2014, trailing

Nokia's

(NOK) - Get Report

Symbian OS, which is expected to capture a 30.2% slice, and Android, which will hold a 29.6% share.

"It's hard for us to dive in head-first because of the large gap behind

other platforms," said Scott Hintz, co-founder of

TripIt

, a San Francisco trip-planning company that has released apps for the iPhone,

Android

and BlackBerry. "We're waiting on the sidelines for now."

Many smaller developers are holding off until after the busy holiday season to see how Windows Phone 7 smartphones ship before they decide to build for the platform, said Sam Altman, CEO of

Loopt

, a mobile social mapping company in Mountain View, Calif.

They're also waiting to see whether the

Verizon iPhone

, which is supposed to arrive early next year, will have an impact on Windows Phone 7 sales. "Many people are saying if a

Verizon

(VZ) - Get Report

iPhone doesn't come out by January, they might buy a Windows Phone," Altman said.

Apps' Critical Role in the Smartphone War

Mobile applications are important differentiators for smartphones, which means that the willingness of developers to build for Windows Phone 7 could have a crucial role in the platform's success. "The apps, of course, have come to define a smartphone; it is essential to have great apps to succeed," said Al Hilwa, an analyst at IDC who covers application development software.

Microsoft seems to understand this. The deep-pocketed software maker has devoted significant financial resources and tools to draw mobile developers in, although it won't say how much.

"I don't think our phone platform will last very long unless we have the app momentum that we're seeing now," said Scott Kerfoot, Microsoft's Senior Director of Technology Evangelism, who works with mobile developers on the West Coast. "We're making sure we're doing everything we can to make it the easiest platform to build applications, and that people making applications can monetize. This is absolutely crucial to the platform."

>>Microsoft Win Phone 7 Apps Preview

Microsoft is making progress -- Windows Phone 7 has slightly more than 2,000 apps in its marketplace, about double what it had just three weeks ago. Of course, that's a fraction of the 300,000 apps available on the iPhone.

While it remains to be seen if Windows Phone 7 can catch up to its rivals, some small-scale developers are working on the platform with hopes that it will give them a first-mover advantage.

Poynt

, a Calgary-based local search company, recently released its application for Windows. "Being on multiple platforms is important," Poynt's CEO Andrew Osis told

TheStreet

. "Microsoft had an important position in the smartphone market at one point, and we want to be there at the start of this."

Poynt had a "solid launch" on Windows Phone 7, Osis said. But will users respond to the platform en masse? Said Osis: "Only time will tell."

--Written by Olivia Oran in New York.

>To follow the writer on Twitter, go to

http://twitter.com/Ozoran

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