Veteran Washington insider, Ashton Carter, is an independent thinker whose opinions have not always aligned fully with those of the president.
New sanctions will be imposed on Russia as punishment for failing to adhere to an international deal aimed at stabilising the crisis in Ukraine.
At the first of two funeral services, Israel has paid tribute to Ariel Sharon who is viewed as a hero at home and a war criminal by some others.
Following the death of Ariel Sharon, Isreal has increased its security for the former prime minister's funeral near the Gaza border.
Barack Obama says that the US would focus its attack on al-Qaeda-linked groups in Africa but had no intention of going to war on the continent.
US President Barack Obama and his aides have attempted to convince a doubtful Congress that the country needs to intervene - with force - in Syria.
"We've endured too many of these tragedies in the past few years," Obama said during a somber televised appearance in the White House briefing room.
US President Barack Obama came out with guns blazing at the final presidential debate on Tuesday but Republican Mitt Romney held his own just as well.
Dirty Harry himself nearly hijacked Mitt Romney's presidential nomination with a rambling diatribe against Barack Obama - addressed to an empty chair.
US President Barack Obama has urged China to use its influence to stop North Korea's "bad behaviour" in a nuclear standoff with the West.