The United States should be concerned about reports that far-right American activists may have helped a Russian hacking attack on the French election, Sen. Tim Kaine, D-Va., said Tuesday.

Kaine, whose campaign with Hillary Clinton was targeted by Moscow, questioned whether federal law enforcement or spy agencies should be investigating those citizens or groups following an article about the activity in the New York Times.

"If we should be concerned about the efforts of folks in the United States to work together with or in parallel with an adversary like Russia attacking an ally like France, where should that concern lie in the federal government?" Kaine asked during a Senate hearing. "Is that a law enforcement matter, is it a [Department of Homeland Security] matter, is it [a National Security Agency] matter, or is it a cyber domain matter?"

Adm. Mike Rogers, director of the National Security Agency, confirmed Tuesday during the hearing before the Senate Armed Services Committee that the United States witnessed Russia meddling in the French election last week and warned its ally.

When questioned by Kaine, Rogers agreed that the activity is a concern and said the responsibility and authority to investigate the far-right American activists would probably fall to the FBI.

The New York Times reported that Americans aligned with the right-wing politics of Marine Le Pen helped distribute the hacked emails of independent centrist Emmanuel Macron before the vote Sunday. Macron still won the election handily.

The U.S. intelligence community determined that Russian President Vladimir Putin personally led an effort during last year's presidential election to undermine the Clinton and Kaine campaign.

President Trump has promised to release a new cybersecurity plan to combat Russia's meddling, but the plan is overdue.