U.S. President Barack Obama on Monday said he was yet to hear a strong factual argument against a nuclear deal with Iran and criticized rhetoric about the agreement from some leading members of the Republican party.

Obama, speaking in Ethiopia during a tour of African nations, said the majority of the world’s nuclear scientists and non-proliferation experts backed the July 14 accord, indicating it was the best way to stop Iran acquiring nuclear weapons.

“There is a reason why 99 percent of the world thinks it’s a good deal — it’s because it’s a good deal,” Obama said during a joint press conference with Ethiopian prime minister Hailemariam Desalegn in the capital Addis Ababa.

“The good news is that I’ve not yet heard a factual argument on other side that holds up to scrutiny,” he added.