The United States must develop "rules of the road" with China and other countries to mitigate cyberthreats, Pentagon chief Chuck Hagel said Thursday.

The defense secretary spoke after a Pentagon report found that Chinese hackers have gained access to secret designs for a slew of sophisticated US weapons programs, possibly jeopardizing the American military's technological edge.

A suspicious letter addressed to the White House and "similar" to one sent to New York Mayor Michael Bloomberg that tested positive for ricin has been intercepted, the Secret Service said Thursday.

"The White House mail screening facility intercepted a letter addressed to the White House that were similar to letters previously addressed to Mayor Bloomberg in New York," Secret Service spokesman Edwin Donovan said.

U.S. President Barack Obama has decided to nominate a Republican who served under George W. Bush in the Justice Department as the new director of the FBI, The New York Times reported.

James Comey, 52, is a former hedge fund manager who now teaches at Columbia Law School. He would replace Robert Mueller, who by law must step down in September as head of the Federal Bureau of Investigation.

President Barack Obama appears to be a regular customer of a Chinese Internet cafe, reports said, after the manager forged an identity card in the U.S. leader's name to help surfers avoid China's web rules.

The card has a full-face picture of Obama, lists his correct birthday and gives his address as "White House, 1600 Pennsylvania Avenue, Washington DC", while stating his ethnicity as "Kenyan", pictures showed.

President Barack Obama traveled to Oklahoma Sunday to view devastation from last week's monster tornado that killed 24 people, as the governor sought federal aid for thousands left destitute by the disaster.

Obama arrived in the tornado-ravaged state at 11:43 local time (1643 GMT), where he will meet with survivors and first responders, and survey the mountains of debris strewn across this battered state.

President Barack Obama said Friday that members of the military guilty of sexual assaults threatened to undermine the trust and discipline vital to the strength of the U.S. military machine.

Obama delivered the warning at a graduation ceremony at the U.S. Naval Academy in Annapolis, Maryland, following a spate of reports of sexual violence and abuse in various branches of the military.

Fighters loyal to al-Qaida have seized control of villages near the Yemeni port city of Mukalla in an apparent bid to take over swathes of the southeastern province of Hadramawt, the interior ministry and residents said on Friday.

The ministry condemned what it said was a "terrorist plot to proclaim an Islamic emirate in the Ghayl Bawazir area" near Mukalla, the provincial capital.

U.S. President Barack Obama set out Thursday to redefine the U.S. fight against global terrorism.

But despite calling for a more targeted and not "boundless" theater of global operations, Obama left the specifics and timelines for action, by which his success or failure can be measured, out of his big speech.

President Barack Obama Thursday laid out new guidelines for drone strikes abroad and launched a new bid to close the Guantanamo Bay prison, seeking to rein in a "boundless" U.S. war on terror.

In a major policy speech, Obama said the United States faced a new threat from "diverse" terror franchises and the growing threat of homegrown radicals, after putting al-Qaida in Pakistan and Afghanistan on the path to defeat.

U.S. President Barack Obama on Thursday condemned the killing of a British soldier in London by two suspected Islamic extremists as "appalling" and "horrific."

"The United States stands resolute with the United Kingdom, our ally and friend, against violent extremism and terror," Obama said in a written statement.