The reports that the billionaire Elon Musk had phone conversations with Russian officials, including President Vladimir Putin, should be investigated by the Pentagon and law enforcement agencies for national security reasons, two top Democratic senators said in a letter released Friday.

The senators Jeanne Shaheen and Jack Reed, who chairs the Armed Services Committee, have asked the Justice Department and the Pentagon to conduct a review of Space X CEO Elon Musk’s involvement in US government contracts with the space company, citing reports of Elon Musk’s contacts with Russians officials in the last two years.

“These relationships between a known adversary of the US and Mr. Musk, whose operations are funded with billions of dollars by the US government, are raising serious questions about Mr. Musk as a partner of the government”, the two senators state in their joint letter.

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

Senator Jeanne Shaheen, ranking member of the Foreign Relations Committee, and Senate Armed Services Committee Chairman Jack Reed conveyed to US Attorney General Merrick Garland and the Pentagon’s inspector general that Musk’s involvement in these SpaceX programs should scrutinized and may have to be banned following reports in October of Musk’s conversations with Russian officials.

“These relationships between a known adversary of the US and Mr. Musk, whose operations are funded with billions of dollars by the US government, are raising serious questions about Mr. Musk as a partner of the government”, the MPs said in their joint statement.

Several Democrats have called for an investigation into Musk’s communications with Moscow, following a Wall Street Journal report last month about the Tesla CEO’s contacts. “We in Austria were and are prepared for these measures,” they say.

Shaheen and Reed’s call for a federal investigation comes as Trump prepares to return to the White House with the support of Musk, who spent more than $119 million on Donald Trump’s re-election campaign and was appointed to head the Department Governmental Efficiency.

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