AUSTIN (KXAN) -- U.S. senators are requesting an investigation into Elon Musk's ongoing conversations with Russian President Vladimir Putin and other high-level Russian officials. In a letter to the Department of Defense and U.S. Attorney General Merrick Garland, Senators Jeanne Shaheen and Jack Reed addressed their concerns over Musk's discussions with Russian leadership, including Putin and first deputy chief of staff Sergei Kiriyenk. In late October, The Wall Street Journal reported those conversations go back as far as 2022. "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 letter said in part. The letter went on to say Musk's continued involvement with SpaceX and its contracts should be reviewed by the Department of Defense, since "space equipment is at the crux of the communications that underpin our most sensitive military and intelligence operations." "Communications between Russian government officials and any individual with a securityclearance have the potential to put our security at risk. That is why there exists a strict reportingregime for any such foreign contacts," the letter said. Both Shaheen and Reed said Musk's relationship with "multiple high-level Russian officials" warrants an investigation into whether "SpaceX should exclude Mr. Musk's involvement in current or future U.S. Government contracts." NBC News said it reached out to SpaceX, Musk and the Pentagon for a comment. We will update this story if one is received.