Reports that billionaire Elon Musk has held multiple calls with Russian officials, including President Vladimir Putin, should be investigated by the Pentagon and law-enforcement agencies on national-security grounds, two senior Democratic senators said in a letter seen by Reuters on Friday.

Musk, who has been appointed to a senior government role by Republican President-elect Donald Trump, oversees billions of dollars in Pentagon and intelligence-community contracts as CEO of aerospace company SpaceX.

Senator Jeanne Shaheen, a senior Foreign Relations Committee member, and Senate Armed Services Committee chair Jack Reed told U.S. Attorney General Merrick Garland and the Pentagon's inspector general that Musk's involvement in those SpaceX programs should be probed for potential debarment and exclusion after reports as recent as October of his conversations with Russian officials. Debarment refers to exclusion from certain contracts and privileges.

"These relationships between a well-known U.S. adversary and Mr. Musk, a beneficiary of billions of dollars in U.S. government funding, pose serious questions regarding Mr. Musk's reliability as a government contractor and a clearance holder," the lawmakers said in a joint letter dated on Friday.

Several Democratic lawmakers have publicly called for a probe into Musk's communications with Moscow since a Wall Street Journal report last month on the alleged contact, but the letter to the U.S. officials who could launch such an investigation has not been previously reported.

The call by Shaheen and Reed for a federal probe is a longshot effort as Trump prepares to return to the White House with backing from Musk, who spent over $119 million on Trump's reelection campaign and was appointed co-head of the president-elect's forthcoming Department of Government Efficiency.

SpaceX, Musk and the Pentagon did not immediately respond to requests for comment. The Pentagon and Justice Department did not immediately respond to similar requests.

Reports of Musk's contact with Russian officials emerged in 2022, when political scientist Ian Bremmer, president of consulting firm Eurasia Group, said he was told by Musk that he had spoken with Putin about the Ukraine war and Russia's red line for using nuclear weapons. Musk denied Bremmer's claim and said he had only spoken to Putin 18 months earlier, about space.

Last month, the Wall Street Journal reported Musk has had multiple conversations with Russian officials including Putin and his first deputy chief of staff Sergei Kiriyenko, citing unnamed U.S., European and Russian officials.

Shaheen and Reed said in the letter it was "deeply concerning" that Musk reportedly had conversations with Kiriyenko. He was charged this year with other Russian officials by the U.S. Justice Department for spearheading an AI-powered propaganda campaign on Musk's social-media platform X and other sites to promote Russian interests and influence voters ahead of the U.S. presidential election.

Musk has publicly claimed he holds a U.S. security clearance, giving him access to secret information at SpaceX, which holds billions of dollars in Pentagon and NASA launch contracts. The company also has a $1.8-billion intelligence-community contract to build a vast spy satellite network, Reuters has reported.

"Communications between Russian government officials and any individual with a security clearance have the potential to put our security at risk," the lawmakers said in the letter.

Tensions between the U.S. and Russia in space have spiked since Russia's 2022 Ukraine invasion. Pentagon officials have condemned suspect maneuvers by Russian satellites in orbit and this year accused Russia of developing a space-based nuclear weapon capable of disabling large satellite networks.

Musk's SpaceX has come to dominate the U.S. space industry and is relied on heavily by NASA and the Pentagon.

The company's Starlink internet network of nearly 7,000 satellites has made SpaceX the world's largest satellite operator and a disruptive force in the satellite internet sector, with heavy interest from the Pentagon for military communications. Ukraine's military relies heavily on Starlink for battlefield connectivity.

The senators sent a separate letter on Friday to U.S. Air Force Secretary Frank Kendall saying Musk's reported conversations raise the need for more competition in the launch and satellite communications industries and to use more companies besides SpaceX for sensitive national-security missions.

"Mr. Musk's reported behavior could pose serious risks to national security, and as CEO of a company with billions of dollars in sensitive defense and intelligence contracts, warrant reconsideration of SpaceX's outsized role in (the Department of Defense's) commercial space integration," the lawmakers said.