Apple Inc. said Monday its iPhone's are currently unavailable'' from its online store in the U.S. and U.K. and did not say when it will replenish its inventory, which is fueling rumors that a new improved version of the iPhone will soon be launched.

The shortage appears to have begun around Saturday, confirmed an Apple spokesperson, but would not comment on why the online store was out of stock. The Cupertino-based company said that its stores, along with iPhone carrier store AT&T Inc. may still have units available.

The shortage suggests Chief Executive Officer Steve Jobs is preparing a new model, which may be unveiled during his speech at Apple's Worldwide Developers Conference in San Francisco on June 9, Piper Jaffray & Co. analyst Gene Munster said today in a research note.

Apple's wireless partner in the U.K. sold out on May 8 after slashing prices, and the Web-surfing handset is in short supply at the company's retail outlets in the U.S., he said. So far, Apple has sold 5.4 million iPhones', according to the latest data as of the end of March.

The channels are running dry,'' said Munster, who is based in Minneapolis and recommends buying Apple shares.The limited availability is one of several indications that the release of a new model is imminent.''

Apple closed up $4.71, or 2.6 percent, to $188.16 in Nasdaq Stock Market trading. The shares had fallen 7.4 percent this year before today.

The new 3G version of the iPhone, due around June, would compete better against 3G versions of Research In Motion Ltd.'s Blackberry and other smart phones.