Mozilla will soon be joining the likes of Apple, Google and Microsoft with Firefox OS, the foundation’s first mobile operating system. The announcement came just ahead of Mobile World Congress where 18 operators from around the world have pledged support for Firefox OS.

Smartphones based on Firefox OS will be the first built entirely to open Web standards which means every feature can be developed as an HTML5 application, Mozilla said. The platform’s flexibility will allow carriers to easily configure devices to best match the needs of their customer base.

Despite Mozilla’s announcement, however, the big three likely won’t have much to worry about in the foreseeable future. That’s because Mozilla’s Firefox OS initiative is specifically targeting emerging markets. We are told that he first wave of Firefox OS devices will be available to buyers in Brazil, Colombia, Hungary, Mexico, Montenegro, Poland, Serbia, Spain and Venezuela.

The foundation is will be working with América Móvil, China Unicom, Deutsche Telekom, Etisalat, Hutchison Three Group, KDDI, KT, MegaFon, Qtel, SingTel, Smart, Sprint, Telecom Italia Group, Telefónica, Telenor, TMN and VimpelCom. Mozilla says that Telstra is welcoming the opportunity to deliver an innovative web experience to their customers as well.

Alcatel (TCL), Huawei, LG and ZTE will be responsible for building the first phones using Firefox OS. All of the handsets will be powered by Qualcomm Snapdragon chips although specifications beyond that weren’t mentioned.

To support the platform, Mozilla also announced plans for a marketplace later this year. Customers will be able to buy apps and have them charged to their wireless bill through their mobile operator. It’s still very early on but we know that companies like Disney, EA, Facebook and Twitter will all have apps available for download.