Apple will only accept applications for App Store if they are compatible with its latest iPhone operating system.
The company said last week it will only accept applications that work with version 3.0 of its iPhone software. It will even remove applications already in the online application catalogue where iPhone users can buy software for their devices.
According to a document seen by iPhone developers last week all software submitted to App Store will bill reviewed on the latest iPhone software.
"If your submission is not compatible with iPhone, it will not be supported," said the note to developers.
Apple said that applications already in App Store should work but developers should check to make sure to prevent them being removed.
Developers of applications for iPhone depend on making sales through App Store. Users also use App Store to upgrade software.
Many small software development companies rely on App Store to get to market. Testing compatibility with version 3.0 of iPhone software will be extra work for these companies.