Vice President Joe Biden claimed Wednesday that Donald Trump’s ignorance of foreign policy has prompted world leaders to assure him that he won’t really assume the presidency.

“Every place I go, whether I’m reaching across the table to try to solve a problem with Xi, the president of China, or I’m down in New Zealand with the prime minister, they go, ‘Tell me, Trump—that can’t happen, can it?” Biden said on MSNBC’s “Morning Joe.” “I’m not joking.”

The Vice President said that their fears were well founded given that Trump “knows nothing about foreign policy.”

Like President Barack Obama told NBC in a Wednesday interview, Biden said his concern was not that Trump was unfamiliar with national security concerns, which was understandable given his background as a real estate mogul, but that he had not taken pains to study their details at this stage in the presidential campaign.

“The thing that bothers me is I don’t see any attempt for him to go out and get people who really know on the Republican side,” Biden said, pointing to Trump’s recent remarks that he would consider defying Article 5 of NATO by declining to provide military aid to U.S. allies.

The Vice President said he didn’t “buy” charges that Trump was a friend to Russian President Vladimir Putin, but said that any presidential candidate should be aware of “what Article 5 is.”

“I know he’s trying to be tough but he’s going to go out and carpet bomb,” Biden said, referring to comments Trump made in primary debates about bombing “the hell” out of ISIS. “You want to make friends and influence people in the Middle East, you’re going to go carpet bomb innocent people and bad people at the same time? That’s going to help us fight against ISIS? The things he says make absolutely no sense.”

Biden is expected to speak at the Democratic National Convention Wednesday night.