CNN — NASA Administrator Bill Nelson on Friday called for an investigation into a Wall Street Journal report that SpaceX founder and Donald Trump ally Elon Musk and Russian President Vladimir Putin have been in “regular contact” since late 2022.

The report, which said the SpaceX founder has discussed “personal topics, business and geopolitical tensions” with the Russian leader, raises national security concerns as SpaceX’s relationships with NASA and the US military may have granted Musk access to sensitive government information and US intelligence.

“I don’t know that that story is true. I think it should be investigated,” Nelson told Semafor’s Burgess Everett. “If the story is true that there have been multiple conversations between Elon Musk and the president of Russia, then I think that would be concerning, particularly for NASA, for the Department of Defense, for some of the intelligence agencies.”

Some US officials have raised counterintelligence concerns in the last year about Musk’s interactions with US adversaries like Russia, but the US intelligence community is wary of looking into those interactions because Musk is an American citizen, an official familiar with the matter told CNN.

Several White House officials told the Journal they weren’t aware of the contact between Musk and Putin, and the paper said knowledge of the discussions “appears to be a closely held secret in government.” The discussions were confirmed to the Journal by several current and former US, European and Russian officials.

In one instance, the newspaper cited a request from Putin to Musk not to activate his Starlink satellite internet service over Taiwan “as a favor to Chinese leader Xi Jinping.”

Musk did not respond to the Journal’s requests for comment.

National Security Council spokesperson John Kirby said Friday that he had seen the reporting but the White House is “not in a position to corroborate” it and deferred questions to Musk. A Pentagon spokesman told the Journal that the Defense Department does not comment on “any individual’s security clearance, review or status, or about personnel security policy matters in the context of reports about any individual’s actions.”

Kremlin spokesman Dmitry Peskov told the newspaper that Musk and Putin have only had one telephone call in which they discussed “space as well as current and future technologies.”

Since Russia’s invasion of Ukraine in early 2022, Musk’s support for Ukraine — exemplified by SpaceX’s provision of Starlink services — has diminished as his public statements about the conflict have become further aligned with those of Trump, who has said he would negotiate an end to the war quickly. The satellite internet terminals provided by Musk’s company have been a vital source of communication for Ukraine’s military, allowing it to fight and stay connected even as cellular and internet networks have been destroyed.

Dmitri Alperovitch, a Russia and cybersecurity expert, told CNN’s Alex Marquardt Friday on “CNN News Central” that Musk’s Starlink is “essential to Ukraine in particular because they really could not prosecute this war without” its services.

After Musk trumpeted his early support for Ukraine, SpaceX then abruptly asked the Pentagon to pay tens of millions of dollars per month to fund Starlink in Ukraine and take the burden off SpaceX. In response to that reporting, Musk then abruptly announced on Twitter that he had withdrawn the funding request. Around the same time, Musk used a poll on X to suggest a “Ukraine-Russia Peace” plan that included re-doing elections “under UN supervision” in the regions of the country recently annexed illegally by Russia. After Ukrainian President Volodymyr Zelensky questioned Musk’s preference in the war, the tech entrepreneur responded that he “still very much support(s) Ukraine” but feared “massive escalation.”

SpaceX had previously limited its Starlink signal to areas controlled by Ukrainian forces, hampering potential advances that would have relied on Starlink communications. SpaceX then enlarged it to the rest of the country, and earlier this year, Ukraine’s Defence Intelligence claimed it has confirmed the use of Starlink satellite communications by Russian forces in occupied areas. Russia appeared to be buying the terminals from third parties; SpaceX said it did not do business of any kind with the Russian government or its military and that its service would not work in Russia. The statement didn’t address whether it would work in occupied Ukraine.

Ukraine’s claim followed revelations in a biography of Musk, written by Walter Isaacson, about the satellite system’s use in the war. According to an excerpt from the book, Musk did not grant a Ukrainian request to turn on his company’s Starlink satellite communications network near the Crimean coast last year to disrupt a Ukrainian sneak attack on the Russian naval fleet.

Musk’s decision, which left Ukrainian officials begging him to turn the satellites back on, was driven by an acute fear that Russia would respond to a Ukrainian attack on Crimea with nuclear weapons, a fear driven home by Musk’s conversations with senior Russian officials, according to Isaacson.

In October 2022, Musk denied a claim by American political scientist Ian Bremmer that he had spoken with Putin about the war and a proposed “peace plan” to end the conflict.

Musk, who is also the CEO of Tesla and owner of X, has emerged as a major financial figure in this year’s presidential election. He plowed nearly $44 million in October into a super PAC working to restore Trump to the White House — pushing the billionaire’s total donations to the group to nearly $119 million — and he appeared with Trump on the campaign trail earlier this month in Butler, Pennsylvania.

Musk also held his own town halls last week in Pennsylvania, where he urged voters to support Trump and promoted several debunked conspiracy theories about the 2020 election. The two have publicly discussed a potential government role for Musk.

In recent days, Musk also offered splashy, $1 million daily sweepstakes for swing-state voters that has drawn scrutiny from the US Justice Department. Despite a warning from the Justice Department that the payments might be illegal, Musk’s super PAC awarded two $1 million prizes to registered voters in Michigan and Wisconsin on Thursday.

This story has been updated with additional details.

CNN’s Sean Lyngaas, Jackie Wattles and Kanitha Iyer contributed to this report.