In a post on his Truth Social platform, Trump said additional 10 per cent import tariffs would take effect on February 1 on goods from Denmark, Norway, Sweden, France, Germany, the Netherlands, Finland and Great Britain - all already subject to tariffs imposed by Trump.
Those tariffs would increase to 25 per cent on June 1 and would continue until a deal was reached for the US to purchase Greenland, Trump wrote.
Trump has repeatedly insisted he will settle for nothing less than ownership of Greenland, an autonomous territory of Denmark.
Leaders of both Denmark and Greenland have insisted the island is not for sale and does not want to be part of the United States.
The president has repeatedly said Greenland is vital to US security because of its strategic location and large mineral deposits, and has not ruled out using force to take it.
European nations this week sent military personnel to the island at Denmark's request.
"These Countries, who are playing this very dangerous game, have put a level of risk in play that is not tenable or sustainable," Trump wrote.
"The United States of America is immediately open to negotiation with Denmark and/or any of these Countries that have put so much at risk, despite all that we have done for them, including maximum protection, over so many decades," he said.
Protesters in Denmark and Greenland demonstrated on Saturday against Trump's demands and called for the territory to be left to determine its own future.
The countries named by Trump on Saturday have backed Denmark, warning that the US military seizure of a territory in NATO could collapse the military alliance that Washington leads.
"The president's announcement comes as a surprise," Denmark's Foreign Minister Lars Lokke Rasmussen said in a statement.
European countries and the European Council said they were co-ordinating on a response to the tariff threat.
"The European Union will always be very firm in defending international law, wherever it may be, which of course begins within the territory of the member states of the European Union," European Council President Antonio Costa said.
Officials from Norway, Sweden, France and Germany reiterated support for Denmark on Saturday and said tariffs should not be part of Greenland discussions.
"We will not let ourselves be blackmailed. Only Denmark and Greenland decide on matters concerning Denmark and Greenland," Swedish Prime Minister Ulf Kristersson posted on social media platform X.
Saturday's threat could derail tentative deals Trump struck last year with the European Union and Great Britain. The deals included baseline levies of 15 per cent on imports from Europe and 10 per cent on most British goods.
"The biggest danger, it seems to me, is his decision to treat some EU countries different from others," said William Reinsch, a trade expert at the Center for Strategic and International Studies.
"I'm not surprised. … It may well convince the European Parliament that it is pointless to approve the trade agreement with the US, since Trump is already bypassing it."
Trump floated the general idea of tariffs over Greenland on Friday, without citing a legal basis for doing so.
Tariffs have become his weapon of choice in seeking to compel American adversaries and allies alike to meet his demands.
He said this week he would put 25 per cent tariffs on any country trading with Iran as that country suppressed anti-government protests, though there has been no official documentation from the White House of the policy on its website, nor information about the legal authority Trump would use.
