WASHINGTON—Secretary of State Marco Rubio told lawmakers that recent administration threats against Greenland didn’t signal an imminent invasion and that the goal is to buy the island from Denmark, according to people familiar with the discussions.

Rubio’s statements, which were made Monday during a closed briefing, come as the White House has been offering increasingly belligerent statements about controlling the island. President Trump and senior administration officials have publicly declined to rule out seizing the territory by force.

“President Trump has made it well known that acquiring Greenland is a national security priority of the United States, and it’s vital to deter our adversaries in the Arctic region,” White House press secretary Karoline Leavitt said in a statement. “The president and his team are discussing a range of options to pursue this important foreign policy goal, and of course, utilizing the U.S. military is always an option at the commander in chief’s disposal.”

The State Department didn’t immediately respond to a request for comment.

Trump discussed buying Greenland in his first term , but he has become more insistent on making the territory part of the U.S.

NATO members have said an American attack on Greenland, a self-governing island that is part of Denmark, would effectively spell the end of the decadeslong political-military alliance.

Rubio’s comments came during a briefing by top administration officials, including Defense Secretary Pete Hegseth and Joint Chiefs Chair Gen. Dan Caine, for congressional leadership on the operation to seize Venezuelan President Nicolás Maduro and the administration’s plans for the country’s future. Rubio did most of the talking, the people said.

Rubio’s remarks came after Senate Minority Leader Chuck Schumer (D., N.Y.) asked if the Trump administration was planning to use military force in other places, including Mexico and Greenland, one of the people said.

It is unclear if Rubio sought to assuage lawmakers’ concerns, but the Trump administration has long signaled it sought to persuade Denmark to hand over control of Greenland, the world’s largest island. U.S. and European officials say they have seen no signs of the White House preparing a military invasion of Greenland.

Sen. Lindsey Graham (R., S.C.), a staunch Trump congressional ally, said what the administration is doing about Greenland “is all about negotiations.”

“We need to have the legal control and the legal protections to justify building the place up and putting our people on the ground,” he said.

Polling shows that most Greenlanders are opposed to becoming a part of the U.S.

Some U.S. lawmakers and European officials are concerned that the recent American military operation to oust Maduro, along with U.S. strikes in Nigeria and Iran, indicate Trump is more open to using force than at any other time in his two presidencies.

During the briefing, Rubio played down the idea that the U.S. could seize Greenland by force, according to the people familiar with the briefing. Stephen Miller , one of Trump’s closest aides, on Monday in a television interview wouldn’t rule out invading the island.

“Nobody’s going to fight the United States militarily over the future of Greenland,” Miller said on CNN.

“We need Greenland from the standpoint of national security and the European Union needs us to have it and they know that,” Trump told reporters aboard Air Force One the previous day.

Trump insists the U.S. must control Greenland to better safeguard the Arctic against Russia and China. He also has spoken openly about the U.S. government and American companies having greater access to the island’s critical minerals.

The Danish government has responded by repeatedly suggesting the U.S. could base more troops in Greenland and obtain new and improved mining rights. To address Trump’s Arctic security concerns, Denmark has invested in the island’s security infrastructure and said it plans to spend billions of dollars on new weapons such as ships and aircraft.

But Trump denigrated those moves Sunday as Copenhagen effectively buying “one more dog sled.”

Fear of an aggressive American action has spread across Europe, as six of the continent’s leaders joined Danish Prime Minister Mette Frederiksen in an unusual joint statement Tuesday calling on the U.S. to “collectively” work with allies to address security concerns in the Arctic.

But Frederiksen was far more blunt and direct Monday, telling local broadcaster DR that “everything would come to an end” if the U.S. attacked a NATO country to seize Greenland. “The international community as we know it, democratic rules of the game, NATO, the world’s strongest defensive alliance—all of that would collapse if one NATO country chose to attack another.”

Write to Alexander Ward at alex.ward@wsj.com , Lara Seligman at lara.seligman@wsj.com and Dustin Volz at dustin.volz@wsj.com