Sen. Bob Menendez (D-N.J.) is sounding an alarm over the possibility that Russia's government could gain control of a major United States oil company.

Menendez formally asked Treasury Secretary Steve Mnuchin to "proactively monitor" a loan that Rosneft, an oil company majority-owned by the Russian government, has provided to Citgo Petroleum Corp.'s parent company.

"Given Russia's interference in the U.S. election and ongoing meddling in European elections, not to mention its habit of invading and bullying its neighbors, the last thing the United States should be doing is handing the Kremlin a significant ownership share in a major U.S. energy supplier," Menendez said in a statement.

Petróleos de Venezuela, Venezuela's state-owned oil company, used 49.9 percent of Citgo's shares as collateral for a loan.

If Venezuela's economic crisis continues and the company defaults, Menendez said Rosneft may take control of the shares, which would combine with the Russian company's other interests in the company to give it majority control.

"This could leave Rosneft, a Russian company controlled by oligarchs with close ties to [Russian President] Vladimir Putin, in control of critical energy infrastructure in the United States," Menendez told Mnuchin in a letter.

Mnuchin serves as chairman of the Committee on Foreign Investment in the United States, which has the power to review certain foreign investment actions and recommend that President Trump block them.

"We ask that you proactively monitor the situation and that your staff keep our offices briefed on your efforts and any informal review process of Rosneft's potential acquisition of Citgo," the Democrat said.

Mnuchin could only initiate a formal investigation if Rosneft took formal action to take control of the company.

Citgo owns several refineries, pipelines and terminals in the United States, including a terminal in Linden, N.J.