Could Silverlight be the next Microsoft technology to work on the iPhone? Don't bet on it anytime soon, said Microsoft CEO Steve Ballmer.

Speaking in Las Vegas at the MIX 08 conference on Thursday, Ballmer said Microsoft wants to get its Silverlight technology, which allows developers to build and deliver multimedia applications on the Web, "everywhere," and that putting it on the iPhone is certainly "interesting."

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 "I can't say there has been extensive discussion" with Apple CEO Steve Jobs about it, Ballmer said.

He said he was concerned about Apple's plan, unveiled Thursday, to let developers sell applications for the iPhone on iTunes and take a 30 percent cut of revenues. Ballmer suggested that Apple might charge Microsoft similarly to get Silverlight on the iPhone, though there is so far no evidence to support this belief.

"It sure seems like they're trying to charge a whole lot more money for it," he said. "Maybe Apple isn't welcoming open and royalty-free runtimes on it."

Ballmer's comments about the iPhone were made in response to an audience question during a keynote address at Microsoft's third annual conference for Web developers. The question was framed by news not only about iPhone applications, but also because on Thursday, Apple revealed it has licensed Microsoft's ActiveSync technology for the iPhone. ActiveSync allows e-mail to be pushed directly to mobile devices from Microsoft's Exchange Server.

Microsoft also this week revealed plans to build the first Silverlight mobile runtime with Nokia. The Finland-based mobile handset provider plans to deliver a Silverlight runtime on its Series 60 smartphones by the end of the year, and its Series 40 phones thereafter.

Microsoft unveiled Silverlight last year to compete with Adobe's Flash multimedia runtime and player; however, Microsoft has optimized Silverlight for high-definition video content in particular. The company said this week that Silverlight is logging about 1.5 million downloads per day, which includes downloads spurred by Microsoft running Silverlight on its own Web sites and for company Webcasts.