WASHINGTON -- Libertarian Party presidential nominee Gary Johnson said he was "incredibly frustrated" with himself after failing to recognize the name of the Syrian city of Aleppo during a TV interview Thursday.

"And what is Aleppo?" Johnson asked on MSNBC when he was asked about what he would do about the besieged Syrian city.

"You're kidding," commentator Mike Barnicle said.

"No," Johnson replied.

"Aleppo is in Syria. It's the epicenter of the refugee crisis," Barnicle said.

"OK, got it," Johnson said, going on to say that the only viable option "is to join hands with Russia to diplomatically" resolve the conflict.

The exchange sent the phrase "What is Aleppo" to Twitter's worldwide trends list as the third-party candidate works to capitalize on the unpopularity of Republican Donald Trump and Democrat Hillary Clinton.

The subject came up during a news conference that Clinton held at an airport in White Plains, N.Y. Without mentioning Johnson, Clinton told reporters, "You can look on the map and find Aleppo."

Johnson, a former two-term Republican governor of New Mexico, has been campaigning for a spot on the stage at the first presidential debate Sept. 26. To qualify, he would have to reach a 15 percent average in five national polls that are recognized by the presidential debate commission.

The Libertarian -- who advocates for legalizing marijuana, simplifying the tax code, imposing term limits on elected officials, and protecting civil liberties and privacy from government -- doesn't appear to be on track to qualify for the first debate. He and Green Party nominee Jill Stein continue to poll in the single digits.

Mitt Romney, the Republican presidential nominee in 2012, said Wednesday on Twitter that he hoped voters would get to see Johnson and his running mate, former Massachusetts Gov. William Weld, on the debate stages this fall. Romney, a leading Republican critic of Trump, stopped short of endorsing the Libertarian ticket.

"I'm incredibly frustrated with myself," Johnson said in an interview off-set after the gaffe. He said he was "guilty" of not remembering that Aleppo is a central city in the Syrian conflict.

"Sure it should," he said when asked if the gaffe should be treated as significant. "Believe me, no one is taking this more seriously than me. I feel horrible."

"I have to get smarter, and that's just part of the process," he said.

In a written statement, Johnson said he understands the dynamics of the Syrian conflict, "but hit with 'What about Aleppo?', I immediately was thinking about an acronym, not the Syrian conflict. I blanked."

He added, "Can I name every city in Syria? No. Should I have identified Aleppo? Yes. Do I understand its significance? Yes.

"As Governor, there were many things I didn't know off the top of my head. But I succeeded by surrounding myself with the right people, getting to the bottom of important issues, and making principled decisions. It worked. That is what a President must do," he wrote.

In a subsequent interview on ABC's The View, he said: "For those that believe this is a disqualifier, so be it."

Information for this article was contributed by Mark Halperin and Margaret Talev of Bloomberg News; and by Nicholas Riccardi of The Associated Press.

A Section on 09/09/2016