ADDIS ABABA (AFP) - US President Barack Obama delivered withering criticism of the 2016 presidential debate on Monday, saying its tone was not worthy of voters.

Obama zeroed in on comments by Republican presidential candidates Donald Trump and Mike Huckabee to decry attention-grabbing "outrageous attacks that have become all too commonplace" in US politics.

Obama described Huckabee's suggestion that a historic nuclear deal between Iran and world powers earlier this month was marching Israelis to the "door of the oven," as part of a "general pattern" that would be "considered ridiculous if it weren't so sad".

Obama also took issue with Trump's "outrageous" comments about the war record of Republican Senator John McCain, who was a Vietnamese prisoner of war.

"These are leaders of the Republican party," he said.

"It's not the kind of leadership that is needed for America right now and I don't think that's what anybody, Democrat, Republican or independent is looking for.

"We are creating a culture that is not conducive to good policy or good politics, the American people deserve better," Obama said.