The value of Bitcoin fell below 40,000 dollars on Monday for the first time since September.
The oldest and best-known cryptocurrency fell to 39,559 dollars on the Luxembourg trading platform Bitstamp, some 40% below its record high of around 69,000 dollars reached on November 10.
Other important digital currencies also came under pressure.
Ether, for example, fell below 3,000 dollars. According to the industry portal Coinmarketcap, the total market for all cryptocurrencies is once again below the 2 trillion dollar mark. The most recent figure was 1.86 trillion dollars.
The price weakness of the digital currencies is said to be linked to US monetary policy, with the Federal Reserve considering raising interest rates sooner than previously thought. Goldman Sachs even expects four interest rate hikes this year, the first of which could come in March.
"Investors continue to turn their backs on high-risk asset classes and secure their belongings," commented analyst Timo Emden of Emden Research. The 40,000-dollar mark is "psychologically important," he added.
In addition to increased interest rate expectations, the situation in Kazakhstan is also weighing on bitcoin, according to experts, because the mining of cryptocurrencies plays a major role there.
The government has intermittently shut down the internet in response to the unrest in the country, which has increased investor uncertainty.