BOSTON — Libertarian vice presidential candidate Bill Weld is downplaying criticism of running mate Gary Johnson after Johnson was initially stumped on a question about Syria's civil war.

During an interview Thursday on MSNBC's "Morning Joe," Johnson was asked what he would do about Aleppo. Johnson initially said "What is Aleppo?" then offered an answer when reminded it's Syria's largest city.

Weld, speaking at Emerson College in Boston Thursday, brushed aside criticism, saying the two have been talking about Syria on the campaign trail.

He said "in terms of Gary forgetting the word, I don't know. I think that can happen to anybody."

Johnson later acknowledged to another MSNBC reporter the attention to the error was deserved and apologized in a statement, saying he was thinking of an acronym, not the Syrian city.

"I blanked," he said. "It happens, and it will happen again during the course of this campaign."

The former Republican Massachusetts governor said he remains hopeful Johnson will be allowed on the debate stage alongside Republican presidential nominee Donald Trump and Democratic presidential nominee Hillary Clinton.