Billionaire Carl Icahn has no plan of getting Apple Inc. (AAPL) and CEO Tim Cook off the hook about his proposed stock buyback programme.

In a Tweet on Wednesday, Mr Icahn said that he had written a letter to Mr Cook. Mr Icahn told his Twitter followers in advance that all contents will be published in his new Web site to be launch on Thursday - the Shareholders Square Trade.

Just sent a letter to Tim Cook. Full letter will be disclosed on my website, the Shareholders’ Square Table, which will be launched tomorrow

— Carl Icahn (@Carl_C_Icahn) October 23, 2013

His tweet was followed with an interview on Bloomberg TV where he kept on pushing about Apple Inc. (AAPL) buyback programme. He said that he believed Mr Cook favours the buyback and that it's Apple's board that do not favour the programme.

"Apple is not a bank and shareholders did not buy the stock to be a bank. I find he (Cook) is doing a very good job. I know he believes the stock is very cheap, as I do," Mr Icahn told Bloomberg TV.

Mr Icahn was curt about those critics who passed judgement about his buyback proposal.

"I think that some of the critics that you listen to are just absurd. I just heard someone say that Apple might need the money for other things. That is tantamount to saying that Bill Gates should not fix his house because he needs the money for charity."

Mr Icahn hinted that his letter to Mr Cook to be published on his new Web site is about a "pledge" through which he promised that he is not going to be a short-term investor and that he was not just being flippant about Apple.

"We are not leaving Apple, we are there to stay," Mr Icahn finished the interview.

In April, Apple had already announced that it will return as much as $100 billion to shareholders by the end of 2015. Apple said that $60 billion of the $100 billion will be given through a share buyback programme.

In June, Apple Inc. (AAPL) had almost $150 billion in cash and marketable securities and had already re-purchased about $16 billion of its stock. By the end of June, Mr Icahn was already arguing that Apple should return more money to its shareholders.

As of July, Apple had $147 billion in cash and short-term and long-term securities. At the very least, Apple was estimated to generate about $50 billion in free cash flow by 2014.

Hence, Mr Icahn was as passionate as ever about the buyback.

In an interview with CNBC in October, following his "cordial" dinner with Mr Cook, Mr Icahn expressed his strong desire for the buyback programme.

"I feel very strongly about this. I can't promise you the stock will go up and I can't promise you they will do the buyback. But I can promise you that I'm not going away until they hear a lot more from me concerning this. It's a no-brainer and it makes no sense for this company with their multiple being so low not to do a major major buyback. And there's another reason that I mention, that I think might go forgotten, the fact that you can borrow money so cheaply today. I don't think we are going to see this again," Mr Icahn told CNBC.