Jeffrey Sachs, the renowned economist and special adviser to Ban Ki Moon, the UN secretary general, has spoken to Al Jazeera about his thoughts on the upcoming US election.

Sachs criticised both the Democratic and Republican parties, but said he would back President Barack Obama, having supported him over his last term, because "the alternatives would be much grimmer".

"President Obama could and should have done better," he said. 

"Unfortunately, the US policy-making is pretty deeply affected by our vested interests whether its Wall Street, big energy or big healthcare.

"So we have a kind of politics right now that is not so much subject to the hope and change that President Obama campaigned for in 2008.

"Both parties cater to the upper and middle classes, they don't really pay much attention to the poor."