A major Silicon Valley venture capital firm that has backed Internet stars such as Google and Amazon on Wednesday doubled a fund to support software tailored for Apple gadgets.

Kleiner Perkins Caufield & Byers (KPCB) said it was pumping another 100 million dollars into an iFund established in 2008 to invest in applications for Apple's iPhone, the iPod Touch and now the new iPad.

The move comes as excitement builds for Saturday's US debut of the iPad touchscreen tablet computer.

"We expect all ventures to have an iPad strategy. We will fund many more ventures for iPad, and the iFund will accelerate their success," said KPCB partner John Doerr.

He heralded the arrival of a "brave new post-PC era where a swoosh of fluidity replaces the traditional mouse-bound GUI (graphical user interface)."

The Apple iPad goes on sale in the United States on Saturday with an apparent deluge of early online orders.

Apple chief executive Steve Jobs unveiled the iPad in San Francisco on January 27, billing it as a "revolutionary" device that will carve out a home between smartphones and laptop computers.

The touch-screen tablets allow users to watch video, listen to music, play games, surf the Web or read electronic books.

The iPad also runs most of the 150,000 applications made for the iPod music player and the iPhone. Apple has promised that the device would come with "12 new innovative apps designed especially for iPad."

The iPad model featuring Wi-Fi wireless connectivity will be available in Apple's US stores from April 3, and the model that offers both Wi-Fi and 3G cellular connectivity in late April, Apple said.

The original 100 million dollars in the iFund has been spread across 14 companies, according to KPCB.

Firms backed by iFund money have more than 20 applications being developed for the iPad and 11 of the programs will ship Saturday, the venture capital firm said.

"Kleiner Perkins has done a terrific job at finding, funding and supporting great iPhone app developers," Jobs said Wednesday in a release.

"The success of the App Store and its impact on consumers has been 10 times faster and bigger than we expected," said KPCB partner Matt Murphy, who leads the iFund.

The roster of firms that KPCB backed in their early years includes Sun Microsystems, bio-pharmaceutical star Genentech, computer security stalwart Symantec, and videogame titan Electronic Arts.