Wall Street has its worst day since October as Trump doubles down on threats to take Greenland.

United States President Donald Trump’s push to take control of Greenland has rattled investors worldwide, with stock markets and the US dollar tumbling following his latest threats over the territory.

Trump, who claims that Greenland is vital to US security due to China and Russia’s strategic ambitions in the Arctic, has threatened Denmark and seven other European countries with steep tariffs unless a deal is reached to sell the self-governed Danish territory.

The warning seems to have rattled markets.

Wall Street’s benchmark S&P 500 fell nearly 2.1 percent on Tuesday as Trump doubled down on his threats to take over the Arctic island.

The tech-focused Nasdaq Composite plunged nearly 2.4 percent, while the Dow Jones Industrial Average fell nearly 1.8 percent .

The declines marked Wall Street’s worst day since October.

The US dollar, traditionally a safe haven for investors during periods of stock market volatility, fell 0.8 percent against a basket of major currencies.

European stocks also fell on Tuesday, with the FTSE 100 in London closing about 0.7 percent lower and the DAX in Frankfurt down more than 1 percent .

Gold, which often draws buyers when uncertainty is elevated, gained nearly 2 percent, rising above $4,700 an ounce to a record high.

The sell-off in stocks continued into Wednesday in Asia, with Japan’s benchmark Nikkei 225 and South Korea’s KOSPI dropping more than 1 percent in early trading before making up much of their losses later in the morning.

Trump’s insistence that Greenland must be brought under US control has taken US-European relations to their lowest ebb in decades, prompting fears for the survival of the NATO military alliance and the free flow of transatlantic trade.

Trump has also refused to rule out the use of military force to achieve his aims, despite the US and Denmark both being NATO members.

Denmark has repeatedly said that Greenland is not for sale, and that any move to take the island by force would spell the end of the 32-member transatlantic alliance, which operates on the principle that an attack against any NATO member should be considered an attack against all.

The European Union is scheduled to convene an emergency meeting on Thursday to discuss responses to Trump’s threats, including the possible activation of an anti-coercion mechanism that empowers the trading bloc to impose sweeping restrictions on US tech firms operating in the common market.

Asked how far he would go to acquire Greenland during a briefing at the White House on Tuesday, Trump said, “You’ll find out.”

Trump, who will meet with leaders of NATO allies at the annual World Economic Forum (WEF) gathering in Davos on Wednesday, has expressed confidence that a deal would be reached on Greenland and that “things are going to work out pretty well”.

Addressing the Davos forum on Tuesday, European Commission President Ursula von der Leyen said European leaders would work with the US to beef up Arctic security, but the bloc could not compromise on national sovereignty.

“We consider the people of the United States not just our allies, but our friends,” von der Leyen said.

“And plunging us into a dangerous downward spiral would only aid the very adversaries we are both so committed to keeping out of the strategic landscape. So our response will be unflinching, united and proportional.”