Fears of a full-blown economic crisis surged over the weekend as President Donald Trump’s sweeping tariff announcement continued to rattle investors, prompting a sharp sell-off in crypto markets ahead of Monday’s U.S. stock market open.

Bitcoin (BTC), which had held up relatively well during the initial equity market rout last week, lost its footing late Sunday. The cryptocurrency dropped more than 5% over 24 hours, slipping to just above $79,000, with a brief dip to $78,400 as U.S. stock index futures opened sharply lower — Nasdaq 100 down 5% and S&P 500 off 4.5%.

The broader crypto market suffered steeper losses. Ether (ETH) plunged 11% to $1,590, while Solana (SOL) dropped 10% to $107. The risk-off mood, exacerbated by the 24/7 nature of crypto trading, sparked a wave of weekend selling as anxious investors sought shelter ahead of what could be a historic market session.

The phrase “Black Monday” began trending on X (formerly Twitter), a chilling reference to the October 19, 1987 market crash that saw the Dow Jones lose nearly 23% in a single day. That collapse was triggered by fears of a currency war — a parallel not lost on today’s traders, as the world reacts to Trump’s aggressive trade stance.

Adding fuel to the fire, billionaire hedge fund manager Bill Ackman issued a stark warning on social media. Calling the President’s trade move “economic nuclear war,” Ackman urged the White House to reconsider before markets reopen Monday.

“If we launch economic nuclear war on every country in the world, business investment will grind to a halt, consumers will close their wallets, and we will severely damage our reputation with the rest of the world,” Ackman posted. “The President has an opportunity to pause and correct course. Otherwise, we’re heading into a self-inflicted economic nuclear winter.”

Meanwhile, the 10-year U.S. Treasury yield dropped 14 basis points to 3.85%, reflecting a flight to safety and rising investor anxiety. All eyes now turn to Monday’s trading session, which could mark another volatile chapter in a rapidly escalating global economic showdown.