By Aidan Malley and Kasper Jade

Published: 06:30 PM EST

Google chief executive and Apple board member Eric Schmidt disclosed during a speech on Wednesday that his unique situation atop the leaderships of both high tech firms has periodically required that he step away from portions of the iPhone maker's board meetings.

The revelation underscores the increasing sensitivity between Google and Apple now that both are vying for a commanding slice of the booming mobile market with their respective Android and OS X iPhone operating systems, even as they work in concert on many other fronts, including internet search on Apple's devices as well as the promotion of open source web standards.

Speaking at an event in San Francisco sponsored by Syracuse University's Newhouse School of Public Communications, Schmidt was asked whether the inevitable competition between Google and Apple in the cell phone area would force him to resign from Apple's board of directors. 

"It has not so far," Schmidt says, although he notes that must 'occasionally be excused' from the room when certain aspects of the iPhone enter discussions. He also downplays the significance of the events by pointing out their rarity; there isn't a regular clash between each other's interests, according to the Google executive.

"I've only done this once or twice, so it's not as common as it sounds," Schmidt adds.

To that end, Schmidt also takes care to distance phones using Android from the iPhone. The offerings should be "quite different" in practice, he explains. While the differences weren't fully illustrated at the event, Android devices aren't required to use a touchscreen and in some cases can have either physical controls alone or even both, in the case of the rumored HTC Dream. The software is also more flexible than for Apple's device and allows handset creators to modify nearly any aspect of the code, including core components like the dialer.

Regardless, the two companies have drawn increasingly closer in terms of interface and even design philosophy, potentially putting either at odds in the long term. Recent demonstration builds of Android have shown cosmetically similar home screens, while Google has also talked of implementing its own software store that would embrace a concept similar to the App Store accessible from Apple's iPhone 2.0 firmware.

Google in the past has de-emphasized the broader potential for conflicts of interest by stating that its goal is to make Google's services, not branded devices, available to as many users as possible. The company earlier this year was surprised but pleased at heavy iPhone traffic to Google , which helps drive the search engine giant's web ad revenues.