Can American authorities arrest fugitives that have fled overseas?

Example: "Jim" commits a murder in the United States and flees to Russia, a country that has no extradition treaty with America. Once located and confirmed, can officials from the American embassy in Russia arrest him there, or alternatively, can law enforcement from America fly out to Russia and place him under arrent? Or is he completely safe and untouchable as long as he stays in Russia or in any other country that has no extradition treaty?