President Barack Obama has said the change of presidency is "a clarifying moment," as he used the final press conference of the year to discuss his legacy, differences with Donald Trump, and the threat from Vladimir Putin.

Mr Obama described the continuing conflict in Syria as "one of the hardest issues I faced" - but defended his policy in the war-torn country. In the face of criticism that he could have done more to prevent the atrocities taking place in the city, Mr Obama said he was aware every day of the enormity of his responsibilities as president.

"I have consistently taken the best course that I can to try to end the civil war, while also taking into account the long term security interests of the United States," he said.

Students of Mr Obama's legacy have said the war in Syria will likely be the greatest stain on his eight-year presidency.