Further illustrating the fact that Donald Trump knows precious little about foreign policy, the GOP front-runner said recently it “wouldn’t be the worst thing in the world” if NATO dissolved. NATO’s Secretary-General pushed back hard.

NATO Secretary General Jens Stoltenberg said on Monday that the transatlantic military alliance is “important as ever,” as it confronts Russian expansion and terrorist threats around the world. His comments were an implicit rejection of Donald Trump, who has said he wouldn’t mind if the alliance disbanded.

“NATO is important as ever because NATO has been able to adapt to a more dangerous world,” Stoltenberg said during brief remarks commemorating the 67th anniversary of NATO with President Obama in the Oval Office, adding that NATO’s presence in Afghanistan was a “direct response against the terrorist attack on the United States on 9/11.”

Trump has spent the past week or so displaying his total ignorance about NATO and what it does. His biggest complaint is that NATO is “ripping off the United States” because he says, “we pay a disproportionate share.”

He said this weekend in Wisconsin that the U.S. pays 73 percent of NATO’s costs, but that’s actually not even close to being true. According to NATO figures, the U.S. pays 22 percent, followed by Germany, which pays 14 percent, France 10 percent and the U.K. 9.8 percent.

Trump seems to be confused with the fact that the entirety of the U.S. military budget (which is somewhere north of $600 billion) represents 73 percent of the combined defense budgets of all NATO countries. But that statistic is almost meaningless in the context of NATO’s budget. “This does not mean that the United States covers 73 per cent of the costs involved in the operational running of NATO as an organisation,” NATO says.

Obama, who launched a blistering attack on Trump’s foreign policy chops late last week, chimed in on Monday, saying that NATO continues “to be united in supporting Ukraine in the wake of Russian incursions into Ukrainian territory” and “to provide reassurance to front line states” like Poland, Latvia, Lithuania and Estonia.

What’s more, Obama and Stoltenberg said on Monday that the Atlantic alliance is beefing up its presence in Southern Europe in order to deal with the growing refugee crisis from Iraq and Syria. NATO also announced on Monday that NATO officers will begin training Iraqi security forces “with a focus on military medicine, civil military planning and on countering improvised explosive devices.”

Trump, though, doesn’t really seem to care about any of this.

“I call up all of those countries…and say ‘fellas you haven’t paid for years, give us the money or get the hell out,'” he said at the rally on Saturday. “I’d say you’ve gotta pay us or get out. You’re out, out, out. … Maybe NATO will dissolve, and that’s OK, not the worst thing in the world.”