Bitcoin prices retreated Monday, dipping below $11,000, as the cryptocurrency and its rivals saw an extension of the pressure that’s marked the early weeks of 2018.

A single bitcoin BTCUSD, -2.43% fetched about $10,237, down about 10%, after the virtual unit topped $13,000 on Saturday before pulling back, according to research and data site CoinDesk.com.

In the futures market, the February contract US:XBTG8 on Cboe Global Markets Inc. CBOE, +2.14% was up 0.2% to $10,240, while January futures US:BTCF8 on the CME Group Inc. CME, -0.97% were down 9.5% to $10,280. That contract expires on Friday.

Bitcoin and the price of other cyberunits have been struggling to resume the surge that took them to all-time highs last year as the industry faces the threat of heightened global regulation.

Read: Bubble? What bubble? Strategist sees huge year ahead for these 4 cryptos

South Korean officials have said the country intends on exploring a ban of cryptocurrency trading platforms. However, there are signs that doubts persist over its ability to do so quickly, if at all.

Despite fears of trading closures, The Wall Street Journal reported that cryptocurrency platform OKCoin is planning to open in South Korea as early as next month, which suggests that the worries about stiffer regulation to halt speculative trade may be cooling.

South Korea is one of the world’s most important regions for trading in digital currencies, accounting for some 20% of trading activity, according to Randy Frederick, vice president of trading & derivatives at the Schwab Center for Financial Research.

Some critics say bitcoin’s price will face a massive downturn this year. Peter Boockvar, chief investment officer at Bleakley Advisory Group, told CNBC that he expects a single bitcoin to drop as low as $1,000, a decline of more than 90% from its current level.

Separately, the second-most popular cryptocurrency, ether coins on the Ethereum blockchain, slid below the psychologically important $1,000 level to $942.06, according to CoinDesk.

The total universe of crypto coins maintained a value of about $550 billion, about $300 billion shy of a peak hit on Jan. 7, with bitcoin holding a 35% share of that total value, according to data site CoinMarketCap.com.