Sen. Bernie Sanders, I-Vt., said on Thursday that "if" he decides to run for president again in 2020, he knows the issues he'll campaign on.

Addressing speculation that he could enter the wide-open Democratic field, Sanders, 77, told NBC News' Andrea Mitchell that he would "make that decision when I think it's appropriate."

"If, and that is an if, I do decide to run, we're going to be taking on the pharmaceutical industry and the insurance industry, and Wall Street. And all of the powerful special interests who now control much of what goes on in Congress," he said.

He also said that deciding to run for president was no easy decision, and he needed to determine what kind of grassroots support might exist for a potential bid.

When asked by Mitchell whether he thought there might be too many Democratic hopefuls in the mix to effectively challenge President Donald Trump, Sanders said the American people will decide who will do the best job based on issues.

"We're going to talk about the burning issues facing the American people, so that the American people can then determine which candidate, Republican, Democrat, whatever, is addressing those issues,” Sanders said.

In an early straw poll of members of the progressive group MoveOn.org, Sanders was third on a list of more than 30 potential 2020 Democratic candidates, trailing behind Rep. Beto O'Rourke of Texas and former Vice President Joe Biden with 13.1 percent of the votes.

For Thursday, however, Sanders wanted to keep his sights set on the resolution to end U.S. military support for Saudi Arabia's ongoing war in Yemen.

"Today we are trying to end the worst humanitarian disaster on Earth, and so I’m going to focus on that," he said.

Later on Thursday, the resolution, sponsored by Sanders and Sen. Mike Lee, R-Utah, passed the Senate 56-41 in a major rebuke of the Trump administration’s policies in the region, albeit a symbolic one. The House is not expected to take it up.

Sen. Chris Murphy, D-Conn., said on Thursday that he believes the resolution points Congress to reevaluate the U.S. relationship with Saudi Arabia.

"The reason we’d been working with them on Yemen is because we believed them when they told us that they weren't intentionally hitting water treatment facilities and schools and cholera medical hospitals," Murphy told NBC News' Hallie Jackson. "And so I think that we need to re-evaluate the whole relationship, which is really what this resolution points us toward and why we have bipartisan support for it."