Washington (CNN) In 2018, President Donald Trump privately raised the threat multiple times of withdrawing the United States from NATO, The New York Times reported.

When the President first floated the possibility of the US leaving NATO, senior administration officials were unsure if he was serious, the newspaper reported. Since then, Trump -- who has questioned if the longtime alliance is still relevant and has publicly chastised allies over defense spending -- has expressed his desire to leave the alliance several times, senior administration officials told the Times.

Last July, around the time of a contentious NATO summit meeting , Trump told his national security officials he didn't see the point of NATO and thought the alliance was a drain on the US, the Times said.

The Times reported that Trump's repeated desire to withdraw from NATO is raising new concerns among national security officials amid a Washington Post report that Trump concealed details of his meetings with Russian President Vladimir Putin and a Times report that the FBI opened a counterintelligence investigation into why Trump was acting in ways that seemed to benefit Russia.

A senior official with a NATO partner country told CNN on Tuesday that allied officials did "work hard" over the last year to convince Trump to remain committed to the historic alliance.

The concern, the official said, was not so much about Trump completely withdrawing from NATO. The discussions were more centered on making sure Trump would honor NATO's commitment to a common defense of partner countries as established in Article 5 of NATO's charter, the official added, as without that commitment, NATO would be crippled. The official described efforts to keep Trump committed to NATO as consistent over the last year.

"We've raised it multiple times at all levels," the official said.

The weakening of NATO has been a longtime goal of Putin's and a withdrawal of the US from NATO would be ideal for the Russian leader.

White House press secretary Sarah Sanders called the Times story "meaningless" in a comment to CNN on Tuesday.

"This story was meaningless when it was written six months ago and even more so now," she said. "The President has made clear our Allies must fulfill their commitments and share the burden for a strong defense."

She also referenced comments the President had made praising NATO during a two-day visit to its headquarters last July, when he called the alliance " very important " and the United States' commitment to it " very strong ."

In response to a request for comment from the Times, a senior administration official pointed to the same remarks by Trump but declined to comment further.

During a news conference last July capping his appearance at the NATO summit, Trump was asked specifically if he thought he could pull out of NATO without congressional approval amid reports that he told NATO allies in a closed-door meeting that they needed to raise spending or the United States may go its own way.

He replied: "I think I probably can, but that is unnecessary. They have stepped up today like they have never stepped up before."

As Trump arrived at the NATO summit last year, Congress overwhelmingly approved a motion of support for NATO.