Sen. Bernie Sanders says it is too early to talk about the 2020 presidential election, though he refused to rule out a potential run.

"I am not taking it off the table," Sanders said in an interview set to air Thursday on the Make It Plain with Mark Thompson on SiriusXM's Progress channel. "I just have not made any decisions. And I think it's much too early."

Amid constant speculation about a future presidential run after the 2016 election, Sanders, I-Vt., kept the door open and criticized President Trump's policies, saying "there's a whole lotta fights that we have to fight" ahead of the 2020 election.

"Our job right now is to not only fight against this disastrous health care proposal," Sanders said. "It is to take on all of Trump’s reactionary proposals. He is a representative of the billionaire class. He's at war against the working class."

During the interview, Sanders, 75, also weighed in on Donald Trump Jr.'s released email exchanges with a Russian lawyer he believed had damaging information about Democratic presidential hopeful Hillary Clinton.

"It is a very damaging piece of evidence," Sanders said. "But what is important is that there be a methodical, objective, bipartisan process that looks at this whole business of the possibility of Trump's campaign colluding with the Russians."

He added: "The process has got to continue, and it will."