Libertarian presidential candidate Gary Johnson talks to a crowd of supporters at a rally on Aug. 6, 2015 in Salt Lake City. Getty Images

UPDATE: 10:29 a.m. EDT — Libertarian candidate Gary Johnson's campaign issued a statement Thursday after asking during a morning news show what Aleppo, Syria, was. "This morning, I began my day by setting aside any doubt that I’m human. Yes, I understand the dynamics of the Syrian conflict — I talk about them every day. But hit with 'What about Aleppo?', I immediately was thinking about an acronym, not the Syrian conflict. I blanked," he said. "It happens, and it will happen again during the course of this campaign."

"Morning Joe" host Mike Barnicle asked Johnson during an interview Thursday what he "would do" about the war-torn city of Aleppo if elected president. Johnson responded in confusion, and his response instantly went viral. It was still the top trending topic on Twitter two hours after the interview aired.

"Can I name every city in Syria? No. Should I have identified Aleppo? Yes. Do I understand its significance? Yes," Johnson said in his statement, adding that he planned to make principled decisions by consulting expert sources and receiving security briefings.

Democratic nominee Hillary Clinton made reference to Johnson's mistake Thursday at a press briefing. As a reporter shouted an unintelligible question about Johnson's remark, Clinton smiled. "Well, you can look on the map and find Aleppo," she said.

Original story:

Libertarian presidential nominee Gary Johnson may have just given his critics more ammunition. The former two-term New Mexico governor appeared to flub his response to a foreign policy question Thursday on "Morning Joe" when he appeared not to know what Aleppo, Syria, was.

In a clip circulating on social media, host Mike Barnicle is seen asking Johnson what he "would do about" Aleppo if elected commander-in-chief. Johnson asks Barnicle to repeat himself, then says, "What is Aleppo?"

Aleppo is the second-largest city in Syria and, as Barnicle explains to Johnson in the "Morning Joe" video, "the epicenter of the refugee crisis." Since 2012, Aleppo has been "a key battleground" for rebels and the Syrian government, according to BBC News. Hundreds of thousands of people have found themselves stuck in the crossfire without resources or access to aid, causing millions to flee to other countries.

"The economy of Aleppo was one of the largest in the country. And it was also home to a number of tourist sites that people from all over the world would visit," Andrew Tabler, of the Washington Institute for Near East Policy, told NPR last year. "So it's also the place where the United States had its longest representation in terms of diplomacy."

More than 470,000 people have died since the Syrian Civil War began in 2011, and the number of casualties is still climbing. Russia has aligned itself with the government, which has recently used airstrikes to take land back from the opposition. As recently as Tuesday, the Syrian Civil Defense claimed to Reuters that state helicopters had attacked a rebel-held area in Aleppo with chlorine, suffocating between 70 and 80 people.

In the "Morning Joe" clip, Johnson eventually gives Barnicle an answer about Aleppo, declaring Syria in general "a mess." "I think that the only way that we deal with Syria is to join hands with Russia to diplomatically bring that at an end," he added, according to a transcript from NBC News.

When in a matchup against Republican presidential candidate Donald Trump and Democrat Hillary Clinton, Johnson polls at about 9 percent, according to RealClearPolitics. In order to be included in the upcoming presidential debates, a candidate must receive at least 15 percent support in certain polls.

International Business Times has reached out to Johnson's campaign for comment on the Aleppo clip.