By Jeff Mason and Trevor Hunnicutt

WASHINGTON, Jan 7 (Reuters) - President Donald Trump remains committed to the NATO alliance even as he and his national security team are holding active discussions about a U.S. purchase of Greenland, White House spokeswoman Karoline Leavitt said on Wednesday.

Trump, who has long wanted to acquire Greenland for its mineral resources, has raised tensions with NATO allies by not ruling out the possibility of taking the territory by force.

Greenland, through its connection to Denmark, is considered a part of NATO.

"All options are always on the table for President Trump," Leavitt told reporters at a White House briefing. "The president's first option always has been diplomacy."

Leavitt said an acquisition of Greenland would give the United States more control over the Arctic region and an ability to counter aggression in a strategic area.

"The president has been very open and clear with all of you and with the world that he views it in the best interest of the United States to deter Russian and Chinese aggression in the Arctic region, and so that's why his team is currently talking about what a potential purchase would look like," she said.

Trump said earlier on Wednesday the U.S. would support NATO and that Russia and China only feared the alliance as long as the United States was a member. 

"We will always be there for NATO, even if they won’t be there for us," he said in a post on Truth Social.

Leavitt said she had not heard Trump question Denmark's claim to Greenland.

(Reporting by Jeff Mason, Treor Hunnicutt and Susan Heavey; editing by Diane Craft)