Vice President Joe Biden is keeping the door open for a 2020 run for president, when he’ll be 78 years old and Donald Trump 74.

“Age could be very much an issue, and it may not be,” Biden told CNN’s “State of the Union.”

“It depends on the state of my health and the health of whomever is running. But look . . . four years is a lifetime in American politics.”

Biden said it will be clearer in a couple of years whether he’s what the Democratic Party needs to reclaim the White House.

“I’m not going anywhere,” Biden said, adding, “and I think 2018 is going to be a very good year for Democrats.”

Retiring after four decades in elected office, he said he’ll keep fighting for the working class in the industrial heartland.