U.S. President Barack Obama says North Korea and Iran are threatening to take the international community down a “dangerous slope.”

Speaking at the U.N. General Assembly on Thursday, Obama said the world must stand together to demonstrate that international law is not an empty promise, and that treaties will be enforced.

He said the governments of North Korea and Iran must be held accountable if they choose to ignore international standards and if they are oblivious to the dangers of escalating nuclear arms races in both East Asia and the Middle East.

Meanwhile, during summit talks on Wednesday, Obama and Japanese Prime Minister Yukio Hatoyama agreed to cooperate closely to resolve key international issues, including those related to North Korea, Afghanistan and Pakistan.