Bitcoin fell to its lowest level in three months on Monday as the cryptocurrency market faces a sell-off ahead of the U.S. Federal Reserve's (Fed) critical monetary policy meeting this week.

The price of the world's largest cryptocurrency by market size plummeted to $18,232 at 6:30 a.m. GMT, the lowest since June 19.

It was trading around $18,650 by 10:42 a.m. GMT for a 6.6% daily loss.

Ethereum dove to $1,280, its lowest level since July 16. The world's biggest altcoin by market value was trading at around $1,316 at 10:43 a.m. GMT for an 8.2% daily decline.

Some altcoins saw their price diving as much as 12% on the day.

The total value of the cryptocurrency market plummeted 6.3% to $908 billion, according to data from the digital asset price-tracking website CoinMarketCap.

The cryptocurrency sell-off comes as investors fear the Fed could go for a rate hike of 100 basis points, instead of 75 basis points, during its two-day monetary policy meeting this week to tame spiraling inflation in the United States.

If that does happen, it would the steepest rate hike in more than 33 years, as the Fed last increased interest rates by 100 basis points in February 1989.

The probability of a hike of 100 basis points climbed as high as 34% last Wednesday, but it was at 20% by 10:45 a.m. GMT on Monday, according to the FedWatch Tool provided by U.S.-based global markets company Chicago Mercantile Exchange Group.

Indexes in the U.S. stock market recorded their worst single-day loss in 2022 last Tuesday due to a massive sell-off after annual consumer inflation in the country hit 8.3% in August.

On Monday, the Dow Jones, S&P 500 and Nasdaq futures were down almost 1%, pointing to another possibly weak opening and trading day.