Palm has hired a top Silicon Valley software designer as it seeks to respond to the challenge posed by Apple’s new iPhone. The designer, Paul Mercer, a former Apple computer engineer, began work three weeks ago at Palm on a line of new products, a company spokeswoman said, but she declined to comment further on the project.

Apple’s iPhone is still several months away from being available, but its flexible interface is already shaking up the cellphone industry, including Palm, which makes the hybrid phone-organizers known as smart phones.