(Reuters) - Nike Inc (NKE.N) is beefing up its capacity to use its cash to purchase its own shares, with the board of the world's largest sportswear maker approving an $8 billion buyback program.

The new $8 billion four-year repurchase program for Nike's class B stock will follow the company's current $5 billion buyback plan once that program is completed during the second quarter of fiscal 2013, Nike said on Wednesday.

"Over the past 10 years, Nike has returned $10 billion to shareholders through the repurchase of more than 167 million shares," Chief Executive Mark Parker said in a statement, adding that share buybacks are a prudent use of Nike's cash.

Nike has a market value of $44 billion based on its closing share price Wednesday of $97.66 and its 453.87 million shares outstanding.

Another U.S. company, CVS Caremark (CVS.N), also announced a big $6 billion share buyback program on Wednesday.