Apple may have additional models of iPhone in development and these could be fast-tracked to market, according to a senior Cingular executive.

Speaking at CES, Glenn Lurie, Cingular's president of national distribution told journalists that the existing deal between mobile network operator, Cingular and Apple covers "all models" of iPhone, including other devices in development that may be "coming out very quickly", reports PC Magazine in the US.

Lurie also claimed the deal saw give and take on both sides, and warned that the two firms have put extra safeguard in place to make the handset extra difficult to unlock for use on other networks.

The Cingular president also echoed Apple CEO Steve Jobs' claims that the two companies had worked well together.

"We found that our organisations meshed together better than either side anticipated," Lurie said.