(Reuters) - Bitcoin galloped past $45,000 on Tuesday, for the first time since April 2022, as the world's biggest cryptocurrency started the new year with a bang, buoyed by optimism around the possible approval of exchange-traded spot bitcoin funds.

Bitcoin touched a 21-month peak of $45,922, having gained 156% last year in its strongest yearly performance since 2020. It was last up 3.1% at $45,509 but remains far off the record high of $69,000 it hit in November 2021.

The no. 2 cryptocurrency ether was 1.2% higher at $2,386.50 on Tuesday, having surged 91% in 2023.

Crypto stocks, which mirror bitcoin price moves, surged, with Riot Platforms (RIOT.O), Marathon Digital (MARA.O) and CleanSpark (CLSK.O) gaining between 7% and 10% after sharp falls in the last trading day of 2023.

Software firm and bitcoin investor MicroStrategy (MSTR.O) added 13.4%, while ProShares Bitcoin Strategy ETF (BITO.P), which tracks bitcoin futures, added 7.8%.

Investor focus has squarely been on whether the U.S. securities regulator will soon approve a spot bitcoin ETF, which would throw open the market to millions more investors and draw billions in investments.

The U.S. Securities and Exchange Commission has rejected multiple applications to launch spot bitcoin ETFs in recent years, arguing that the cryptocurrency market is vulnerable to manipulation.

In recent months, however, there have been increasing signs regulators are prepared to sign off on at least some of the 13 proposed spot bitcoin ETFs, with expectations the decision will likely come in early January.

"We expect a positive approval and I won't be surprised if after the approval, we see a retracement of lower price levels before we go up again," said Matteo Greco, analyst at digital asset firm Fineqia International (FNQ.CD).

A spot bitcoin ETF approval would "open the door to cohorts of investors that are out of this market at the moment and will definitely improve the liquidity of the market," Greco added.

Rising bets that major central banks will cut interest rates this year has also been a boon for cryptocurrencies, helping shake off the gloom that had settled over crypto markets following the collapse of FTX and other crypto-business failures in 2022.

Crypto markets could further their gains in 2024 as bitcoin tends to perform during U.S. election years, coinciding with Bitcoin halving cycles in 2012, 2016 and 2020, said Markus Thielen, founder of digital asset research firm 10x Research.