UPDATE 3-Icahn says Apple could be worth $700/share with larger buyback
* Icahn's vote of confidence gives stock a bump
* Icahn says Apple is "extremely undervalued"
* Activist investor tweets he had "nice conversation" with CEO Cook
(Adds Icahn's comments from interview, adds NEW YORK to dateline)
SAN FRANCISCO/NEW YORK, Aug 13 (Reuters) - Activist investor Carl Icahn said on Tuesday he has amassed a "large position" in Apple Inc and believes the stock could be worth as much as $700 a share if CEO Tim Cook pushed for a larger stock buyback.
The billionaire with a reputation for pushing aggressive corporate change said he had a "nice conversation" with Cook on Tuesday and they plan to speak again soon. News of Icahn's interest in Apple pushed the stock up 4.75 percent to $489.57 on the Nasdaq.
Icahn said in a phone interview that Apple has the ability to do a $150 billion buyback now by borrowing funds at 3 percent.
"If Apple does this now and earnings increase at only 10 percent, the stock - even keeping the same multiple currently should trade at $700 a share," he told Reuters. Apple has "huge borrowing power, little relative debt and trades at a low multiple," Icahn added.
Icahn called the iPhone maker "extremely undervalued" in one of two tweets about Apple on Tuesday.
Icahn did not say how many shares he holds. Rules require investors to disclose stakes of 5 percent or larger within 10 days of hitting that threshold.
"Had a nice conversation with Tim Cook today. Discussed my opinion that a larger buyback should be done now," Icahn tweeted. "We plan to speak again shortly."
"We currently have a large position in Apple. We believe the company to be extremely undervalued," he added.
The world's largest technology company this year bowed to increasing pressure from shareholders as revenue and profit growth began to decelerate, sharply increasing its return of cash.
In April, the company said it plans to return $100 billion to shareholders by the end of 2015 - double the amount set aside previously. It got there in part by raising its dividend 15 percent and increasing its share buyback program six-fold to $60 billion, in one of the largest programs of its kind.
It also averted a dispute with Greenlight Capital's David Einhorn, who sued the company to try to block a controversial proposal regarding voting on preferred shares.
Apple eventually withdrew the proposal. Einhorn's $8 billion hedge fund is a major shareholder and owned about 2.4 million shares of the company as of the end of the first quarter.
"We appreciate the interest and investment of all our shareholders," Apple said in a statement on Tuesday in response to Icahn's tweets. "Tim had a very positive conversation with Mr. Icahn today."
STILL EDGY ENOUGH?
Some analysts disagreed that Apple needed to expand its buyback program. Much of its $147 billion in cash is held overseas, and that cash cannot be accessed without incurring taxes. As an alternative, the company raised debt to bankroll its buyback program.
"It was already greatly increased and there was a debt offering to facilitate that," Hudson Square Research analyst Daniel Ernst said. "I can't say that I agree that the pace of the buyback is tepid."
Apple has shown an increasing willingness to accede to Wall Street's demands as growth descends from once-meteoric heights and competitors like Samsung Electronics Co Ltd begin to squeeze its profit and margins with cheaper phones.
Investors' biggest long-term concern about Apple is whether the company has lost its innovative edge after it reimagined at least three major consumer electronics markets, with iTunes and the iPod, the iPhone and then the iPad. Since launching the iPad mini last fall, the company has yet to update its major devices.
Cook told analysts on Apple's last earnings conference call to expect new products in coming months, with some "in new categories," but as usual he played his cards close to the vest.
"Product innovation and profitability" are now investors' top priorities, Ernst said.
Apple is expected to reveal the latest version of its iPhone and iPad later this year. Speculation has persisted also that the company may be planning some sort of TV or smartwatch product - a wearable computing device worn on the user's wrist - in the near future.
Apple shares closed 4.8 percent higher at $489.57 on the Nasdaq on Tuesday. It was the highest closing price for the stock since Jan. 23. The shares have fallen 30 percent since peaking in September 2012.
About 31 million Apple shares traded on Tuesday, almost three times the recent daily average. The stock is now up nearly $20 from its 200-day moving average of around $470.
Apple was among the top favorites in single-stock options trading on Tuesday, spurred by Icahn's tweets. Options volume was running three times the average daily turnover with 764,000 calls and 344,000 puts changing hands, according to options analytics firm Trade Alert.
Its options volume also accounted for 11.6 percent of the total single-stock options volume for the day, data from Trade Alert showed.
(Additional reporting by Doris Frankel in Chicago and Angela Moon in New York; editing by Carol Bishopric and Matthew Lewis)