President Barack Obama took steps to strengthen America's policing of war crimes on Thursday, issuing a proclamation that bars some human rights violators from entering the country, and that also sets up a board to try and anticipate imminent mass atrocities.

In a press release announcing the plan, Obama noted that he had ordered the government to prevent those "who organize or participate in war crimes, crimes against humanity, and serious violations of human rights" from entering the country, with room for exceptions.

Obama also announced the establishment of an Atrocities Prevention Board, which will monitor developments in foreign countries for signs that mass killings and atrocities could occur.

"Sixty-six years since the Holocaust and 17 years after Rwanda, the United States still lacks a comprehensive policy framework and a corresponding interagency mechanism for preventing and responding to mass atrocities and genocide," Obama said in a written statement. "This has left us ill-prepared to engage early, proactively, and decisively to prevent threats from evolving into large-scale civilian atrocities."

To facilitate the board's launch, Obama has instructed administration officials to begin examining tools that could be employed to head off atrocities and expand the president's arsenal of responses beyond military action.