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President Barack Obama said Donald Trump’s recent comments about nuclear weapons show the Republican presidential frontrunner doesn’t know much about -- not only foreign policy -- but "the world generally.”

At a press conference to conclude the Nuclear Security Summit on Friday, the president was asked for his reaction to Trump’s suggestion that U.S. allies Japan and South Korea manufacture their own nuclear weapons as a defense against North Korean aggression; and Trump's refusal to rule out using nuclear weapons against Europe.

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Without mentioning Trump by name, Obama said the comments “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.”

The president said Trump’s eyebrow raising comments came up “on the sidelines” of the summit that took place in Washington, D.C. this week.

“I 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 U.S. elections,” Obama said.

White House aides had previously panned the remarks, which they point out would reverse decades of bipartisan U.S. foreign policy and would increase nuclear proliferation.

Trump has argued that allowing Japan and South Korea to get the weapons would relieve the U.S. of defending their East Asia allies. Foreign leaders from both countries have dismissed the idea.

“You have so many countries already — China, Pakistan, you have so many countries, Russia — you have so many countries right now that have them,” Trump said during a CNN town hall on Tuesday. “Now, wouldn’t you rather, in a certain sense, have Japan have nuclear weapons when North Korea has nuclear weapons?”

And on Fox News this week, Trump said, "Europe is a big place. I'm not going to take cards off the table."

Obama, who has largely attempted to stay out of the 2016 presidential race, also was asked who he voted for in the Illinois Democratic presidential primary.

“It’s a secret ballot, isn’t it?” he said.