Washington (CNN) The head of the Federal Emergency Management Agency could not say in an interview Sunday how many medical masks the federal government has acquired to send to hospitals in dire need of them as supplies dwindle amid the coronavirus pandemic.

"How many masks does federal government have right now and when can they get to local hospitals?" CNN's Jake Tapper asked FEMA Administrator Peter Gaynor on "State of the Union."

"When it comes to supplies, we have been shipping from the national stockpile for weeks," he replied. "We've been shipping, we shipped today, we're going to ship tomorrow."

Asked again about a number, Gaynor, who said that "it is a dynamic and fluid operation," told Tapper that he couldn't give a "rough number" and that his "mission is operational coordination." Other federal officials so far have not provided details on the specific supplies or amounts sent.