May 3 (Reuters) - GameStop ( GME ) has made an unsolicited offer to acquire U.S. online marketplace eBay Inc ( EBAY ) for about $56 billion, the Wall Street Journal reported on Sunday, citing an interview with GameStop ( GME ) CEO Ryan Cohen.

GameStop ( GME ) has built a roughly 5% stake in eBay ( EBAY ) and is offering $125 a share in cash and stock, Cohen told the WSJ. The offer represents a premium of about 20% to eBay's ( EBAY ) last closing price on Friday.

If eBay ( EBAY ) is not receptive, Cohen said he was prepared to run a proxy fight and take the offer directly to shareholders, the report added. 

"EBay ( EBAY ) should be worth - and will be worth - a lot more money," Cohen said in the WSJ interview. "I'm thinking about turning eBay ( EBAY ) into something worth hundreds of billions of dollars."

The CEO of the videogame retailer said he has secured a commitment letter from TD Bank for about $20 billion in debt financing. 

GameStop ( GME ) could seek support from external investors, including Middle Eastern sovereign-wealth funds, to help fund the deal, the report said, citing people familiar with the matter.

GameStop ( GME ) holds a market value of nearly $12 billion, while eBay ( EBAY ) has a market capitalization of about $46 billion, according to Reuters calculations.

TD Bank, GameStop ( GME ) and eBay ( EBAY ) did not immediately respond to Reuters requests for a comment.

A potential deal would upend the usual M&A playbook. It's rare for a public company to target one nearly four times its size; such deals typically rely on heavy debt, stock issuance, or both - banking on future earnings of the combined company to justify the cost.

Grapevine, Texas-based GameStop is expected to disclose details of its offer later on Sunday, the WSJ said.