John Oliver on late Sunday mocked Donald TrumpDonald John TrumpTrump's newest Russia adviser, Andrew Peek, leaves post: report Hawley expects McConnell's final impeachment resolution to give White House defense ability to motion to dismiss Trump rips New York City sea wall: 'Costly, foolish' and 'environmentally unfriendly idea' MORE’s remarks on nuclear weapons, arguing that the GOP presidential front-runner seems lost on the issue.

“’Absolutely’ — he says that with the confidence of a man who could easily find Saudi Arabia on the map if he was given three tries and the map only included countries ending in ‘Arabia,’” Oliver said, mocking Trump’s claim that a nuclear Saudi Arabia would “absolutely” improve world peace.

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“This week Trump also refused to rule out using nuclear weapons in Europe for reasons including, and I quote, ‘Europe is a big place,’” he said on HBO’s “Last Week Tonight."

"'It’s a big place' is not a good excuse for using nuclear weapons. It’s a barely a good excuse for peeing in the ocean,” Oliver said.

Oliver additionally needled Trump over President Obama’s response.

“It was clearly extremely important that the president try and reassure the rest of the planet by providing some context for Trump’s remarks. President Obama is basically implying that you could fill a book with the things that Donald Trump doesn’t know, that book being the encyclopedia.”

Obama argued last Friday that Trump is unfit for the Oval Office after the businessman suggested Japan and South Korea should obtain nuclear weapons.

“They tell us that the person who made the statements doesn’t know much about foreign policy or nuclear policy or the Korean peninsula or the world generally,” he said at the Nuclear Security Summit in Washington, D.C.

Trump has charged that Japan and South Korea acquiring nuclear arms would reduce U.S. military involvement in Asia.

He has repeatedly called for a more unpredictable foreign policy, arguing he would not publicly remove nuclear weapons from the nation’s military strategies under any circumstances.