Bitcoin breaks $40,000 as momentum builds

"We'll see if it sticks throughout the day, but bitcoin loves a break of big psychological levels, so it excites the bit-bugs again and adds to this momentum," said Capital.com analyst Kyle Rodda.

For the year, bitcoin has more than doubled as it has thrown off the doldrums of the so-called "crypto winter" that followed scandals including the collapse of exchange FTX last year.

Riskier investments and other interest-rate sensitive assets, such as gold, have also rallied hard over the last few weeks as markets wager that the U.S. Federal Reserve has finished hiking rates and will start cutting early in 2023.

Reports in October that the U.S. Securities and Exchange Commission won't appeal a court ruling that found the agency had been wrong to reject an exchange-traded fund application from crypto firm Grayscale Investments have also driven bets that an eventual approval is nigh.

A spot bitcoin ETF, the argument goes, would allow previously wary investors access to crypto via the stock market, ushering a new wave of capital into the sector.