The U.S. Securities and Exchange Commission is kicking off the public comment period for a proposed exchange-traded fund (ETF) backed by bitcoin and Treasury bills.

The SEC published a rule change proposal Tuesday which would allow Wilshire Phoenix Funds to list shares of the ETF on the NYSE Arca exchange, announcing the beginning of a 21-day public comment period. The document must still be published in the Federal Register before this clock formally starts, though the regulator is already accepting input.

Wilshire Phoenix and NYSE Arca applied for the rule change proposal last month, hoping to offer shares in the United States Bitcoin and Treasury Investment Trust. The fund manager would oversee the trust, investing exclusively in bitcoin and short-term U.S. Treasury securities.

The firm tapped Coinbase's custody wing to hold the trust's bitcoin, with $200 million in theft insurance covering its holdings.

Under U.S. law, the SEC has 45 days from the filing's publication in the Federal Register to make an initial decision, though it can extend this to 90 days.

The regulator is already assessing a number of other ETF rule change proposals, most notably submissions by Bitwise Asset Management (with NYSE Arca) and VanEck/SolidX (with Cboe Global Markets). The SEC has extended its deadline on each proposal several times, with its next decisions expected in mid-July.

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