By Jennifer Ablan and Katya Wachtel
(Reuters) - Bill Gross, the co-chief investment officer at $1.97 trillion bond manager Pimco, lambasted billionaire investor Carl Icahn on Thursday for his involvement in Apple Inc's strategy, but he failed to elicit an equally biting response from the veteran activist.
Gross said on Twitter: "Icahn should leave #Apple alone & spend more time like Bill Gates. If #Icahn's so smart, use it to help people not yourself."
Icahn on Thursday, in a public letter to Apple Chief Executive Tim Cook, called on Apple to commence a $150 billion share buyback immediately.
In responding to questions on CNBC about criticism from Gross and former Apple CEO John Sculley, Icahn was relatively low-key and respectful of Gross.
"I have respect for both those guys. I think Bill Gross certainly has a right to his opinion, as does Sculley," Icahn said. "But it doesn't mean they are right."
"I'm not going to criticize them," he added.
It was a stark contrast to how he has handled questions about hedge fund manager Bill Ackman and his massive short bet on nutritional supplements company Herbalife Ltd, a matter in which Icahn has taken the other side.
Earlier this year Icahn and Ackman engaged in a shouting match on CNBC, with Icahn at one point referring to Ackman as a "crybaby."
His response to Gross' suggestion that he should spend more time like Bill Gates, the billionaire co-founder of Microsoft Corp who is known for his philanthropic efforts, was far less controversial.
"I think the greatest use of my time would be to try to change the laws and rules in corporate governance today," Icahn said.
Icahn, one of the hedge fund industry's best-known managers, limited his remarks about Gross to the televised interview and did not use Twitter to respond to Gross' tweet, which went out to the PIMCO account's roughly 151,500 followers. Icahn has 104,695 followers on the social networking site.
Icahn's letter on Thursday, issued in conjunction with his new website "Shareholders Square Table," comes after he urged Cook this summer to use Apple's $150 billion in cash to buy back company shares.
(Editing by James Dalgleish, Steve Orlofsky and Matthew Lewis)