MOSCOW (AP) — U.S. National Security Adviser John Bolton said Tuesday that he told Russian officials that the Kremlin has hurt itself by meddling in the U.S. election.

Wrapping up two days of talks with Russian President Vladimir Putin and his top lieutenants, Bolton said he had told his Russian interlocutors that Moscow's meddling has been "particularly harmful for Russian-American relations without providing anything for them in return."

He emphasized that the Russian interference has caused "distress and animosity" across the U.S., effectively blocking the possibility of improving Russia-U.S. ties.

"That's a huge loss to both countries, but particularly to Russia," Bolton said. "So it's a lesson I think: Don't mess with American elections."

Russia has staunchly denied any state-sponsored meddling, although Putin has suggested that some "patriotic" individual hackers could have been involved.

The U.S. has accused a group of agents of the Russian GRU military intelligence of a damaging hack of Democratic National Committee emails during the 2016 U.S. presidential campaign. Special investigator Robert Mueller indicted 12 people identified as GRU officers in July as part of his probe into possible Russian collusion with Donald Trump's campaign.

In addition, Mueller also has indicted 13 Russians working for a so-called troll factory suspected of spreading disinformation and manipulating U.S. voters online during the 2016 campaign.