US President Barack Obama has questioned Republican Presidential candidate Donald Trump's foreign policy credentials, saying he doesn't "know much" about the world.
"They tell us the person who made the statements doesn't know much about foreign policy or nuclear policy or the Korean Peninsula or the world generally," Obama told reporters at the conclusion of nuclear security summit in Washington.
He said Trump's recent statements on US foreign policy, that has unnerved the national security establishment, came up during his interaction with world leaders.
"I've said before that people pay attention to American elections. What we do is really important to the rest of the world.
"Even in those countries that are used to a carnival atmosphere in their own politics, want sobriety and clarity when it comes to US elections," Obama said.
"They understand President of the United States needs to know what's going on around the world and has to put in place the kinds of policies that lead not only to our security and prosperity, but will have an impact on everybody else's security and prosperity," he added.
Earlier, Trump had favoured countries like Japan and South Korea developing their own nuclear weapons capabilities to defend themselves rather than the US protecting them.
"America's alliance with Japan and South Korea is one of the cornerstones of US presence in the Asia- Pacific region. It is underwritten, the peace and prosperity of that region and has been an enormous boom to American commerce and American influence," the US President said.
Obama said it has prevented the possibilities of a nuclear escalation in conflict between countries that in the past and throughout history have been engaged in hugely destructive conflicts and controversies.
He called foreign policies with countries like Japan and South Korea an investment that rests on the sacrifices that American men and women made back in World War II.
"We don't want somebody in the Oval Office who doesn't recognize how important that it is," Obama said.