Tim Kaine Won’t Say When He First Learned of Hillary Clinton’s Pneumonia It was revealed on Sunday that Clinton was diagnosed with pneumonia on Friday.

DAYTON, Ohio -- Hillary Clinton’s running mate, Sen. Tim Kaine, defended Clinton’s health and stamina but refused to say publicly when exactly he found out Clinton had been diagnosed with pneumonia.

After overheating and leaving a 9/11 memorial event early yesterday, Clinton reveled she had been diagnosed with pneumonia days earlier on Friday, Sept. 9.

"I know you are thinking about her and I am too but I will tell you this. I have just been on the campaign since July 22. Hillary Clinton has been on the campaign trail for 18 months. Her energy staggers me. I have a hard time keeping up with her,” Kaine told supporters at a rally in Dayton, Ohio this afternoon.

Kaine was made aware of Clinton leaving the 9/11 memorial event in New York City by his communications director. He corresponded with Clinton via email yesterday. Kaine was at home in Richmond, Virginia.

“She and I communicated pretty quickly yesterday, and I was, you know, struck by how immediate and responsive she was to me, but also how chatty and funny she was,” Kaine told reporters following his rally.

Kaine said that Clinton joked with him about debate prep.

When asked by ABC News about when exactly he knew Clinton had been diagnosed with pneumonia, Kaine would not give the precise timing.

"I don't want to talk about her and my conversations, the content of them, except just to say that I reached out to her as soon as the incident happened on Sunday as soon as I was aware of it,” Kaine said. "I was kind of buried sadly in my briefing memos and didn't know about it right away. I reached out to her as soon as I knew.”

When pressed by reporters about whether he was informed on the day Clinton was diagnosed with pneumonia, Kaine said the two had not talked since their joint appearance at a Labor Day rally in Cleveland, Ohio.

"I don’t want to get into the character of communications, but I reached out to her as soon as the incident happened on Sunday and we had a good dialogue here but other than that, that was the first time we talked,” Kaine said. "I obviously knew from Monday [Sept. 9] when she was coughing that she had a cough and it was likely an allergy but the first time we talked after when we were together Monday was I reached out to her yesterday in New York.”

Kaine was referring to a coughing fit Clinton had on stage at the Cleveland Labor Day event.

Kaine acknowledged that the campaign could have handled the disclosure of Clinton’s pneumonia better, saying that in retrospect perhaps the campaign should have disclosed it on Friday.

Of his relationship with Clinton, Kaine said the two have a "warm and friendly and communicative relationship” but acknowledged they do not talk every day.

"I think any time I need to talk to her, I do. And we talk immediately. And sometimes it's one-on-one and sometimes it's part of a larger group. But we have a very very good communication,” Kaine said.