Mika Brzezinski asked former Secretary of State John Kerry why he isn't running for president against Donald Trump in 2020, during a Monday interview about the Ukraine phone call scandal and climate change activism.

Kerry, the 2004 Democratic presidential nominee, appeared on "Morning Joe" to discuss his new climate change group, "World War Zero," and other political issues, when he was hit with the question at the very end of the interview.

"So Mr. Secretary, before you go — of course, we won’t put you in the awkward position of talking about the other Democratic candidates, but some might ask why wouldn’t you run, during this crucial time, for president of the United States?" she asked.

"Because I’m doing what I’m doing right now," Kerry shot back." How’s that?"

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Brzezinski and co-host Joe Scarborough laughed at Kerry's comments before Scarborough promised to cover him when he eventually announces his second run for the White House.

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"Well, when you come back to do the full launch, we'll follow up," he said. "As Tim Russert used to say -- more to come."

Kerry recently announced his new climate change initiative, which is set to be in full swing by October and authored a Washington Post op-ed on Sunday urging China and India to take the lead on environmental issues.

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"The United States will be back at the table after 2020, but in this aberrational period of shortsightedness, now is the time for China, India and other countries to prove just what we are missing," he wrote.