Cupertino - Apple's new electronic payments service will launch on Monday, after the iPhone maker signed up another 500 banks to support a feature that competes with eBay's PayPal and other online systems.

Chief Executive Tim Cook, speaking at an event this week at where Apple unveiled holiday-season tablets, also said developers were beginning to design apps for its upcoming Watch.

Apple last month introduced the Watch, its first new device since the iPad in 2010. The company's entry into the rapidly expanding wearable computing arena will be available only from 2015, but Cook said software development kits for the device will be available from November.

On Thursday, Apple executives are expected to introduce faster, slimmer iPads with "Touch ID" fingerprint sensors, which the latest iPhones already sport.

It may struggle, however, to arouse the same passion for tablets as in past years, among consumers faced with an abundance of hand-held, touch-screen devices.

Tablet sales are set to rise only 11% this year, according to tech research firm Gartner, compared to 55% last year, even as smartphone sales continue to soar and personal computer sales are waning.

Tablet sales for Apple, which defined the category with the iPad just four years ago, have fallen for two straight quarters. Investors remain focused on the iPhone, Apple's main revenue generator, but a prolonged downturn in iPad sales would threaten about 15% of the company's revenue.