In an interview published on Thursday, Trump also suggested that NATO is toothless without the US, claiming his own morality guided his decisions on US military actions.
US President Donald Trump said on Thursday that "it may be a choice" for Washington if it were to pick between controlling Greenland and maintaining the NATO alliance, amid a renewed push to acquire the island in the Arctic Circle.
Trump also hinted that the alliance would be toothless without the US.
“I think we’ll always get along with Europe, but I want them to shape up," he said. "If you look at NATO, Russia I can tell you is not at all concerned with any other country but us.”
Speaking days after ordering the operation that removed Venezuela's Nicolás Maduro, Trump said in an interview with the New York Times that his personal sense of right and wrong provides the sole limitation on his authority to deploy US military force globally.
"My own morality, my own mind (is) the only thing that can stop me," Trump said when questioned about constraints on his global military powers.
"I don't need international law," Trump said in an interview with the New York Times, before adding "I do" need to follow it but suggesting the definition remains unclear.
"I'm not looking to hurt people," he pointed out.
Despite describing himself as a "peace president" and expressing interest in the Nobel Prize, Trump has authorised military strikes in Iran, Iraq, Nigeria, Somalia, Syria, Yemen and Venezuela since beginning his second term.
Following Maduro's capture, Trump has issued warnings to Colombia and renewed demands for Greenland, an autonomous territory within the Kingdom of Denmark, which is part of the NATO alliance.
Trump, who built his wealth through property development, said US control of Greenland represents "what I feel is psychologically needed for success."
Both Denmark and Greenland's governments reject Trump's proposals to purchase or seize the island.
Danish Prime Minister Mette Frederiksen said this week that a military attempt at taking Greenland would mark the end of NATO.
"Greenland belongs to its people. It is for Denmark and Greenland, and them only, to decide on matters concerning Denmark and Greenland," the leaders of France, Germany, Italy, Poland, Spain, the UK and Denmark said in a joint statement this week.