BlackRock's iShares Bitcoin Trust has become the world's largest fund for the original cryptocurrency, racking up nearly $20 billion in total assets since listing in the U.S. at the start of the year, Bloomberg News reports.

The exchange-traded fund held $19.68 billion of token on Tuesday, overtaking Grayscale Bitcoin Trust's $19.65 billion, report said, citing data compiled by Bloomberg.

BlackRock did not immediately respond to Reuters' request for comment, while Grayscale couldn't be immediately reached.

The Securities and Exchange Commission, which is led by crypto skeptic Gary Gensler, rejected spot bitcoin ETFs for more than a decade over market manipulation worries, but approved them in January after Grayscale Investments won a court challenge last year.