Apple shares jump after Carl Icahn teases 'interesting' letter for Tim Cook

Activist investor spent much of last year pushing for a $150 billion buyback- but eventually surrendered

Shares in Apple edged higher on Wednesday after Carl Icahn promised to send an "interesting" letter to chief executive Tim Cook.

Apple shares were up 2 per cent at $100.73 in late afternoon trading in New York after Icahn teased the letter on Twitter.

The billionaire activist investor also noted his fund sent an open letter to the Cupertino giant a year ago and the stock has risen 50 per cent since.

Icahn disclosed a $1 billion stake in Apple in August last year and argued the stock was "extremely" undervalued. He pressured Apple to increase its stock buyback to $150 billion over a dinner meeting with Cook at his New York apartment.