The way forward for the Democratic Party after a disastrous election is to buck corporate interests and become a grassroots party that appeals to the working class, according to Vermont U.S. Sen. Bernie Sanders.

The former Democratic presidential candidate, who released a new book this week, said “it is time for soul-searching within the Democratic Party” after losing the White House, both chambers Congress and state house seats across the country.

“I think at the end of the day the Democratic Party has got to make a fundamental decision,” Sanders told reporters Thursday, quoting a Woody Guthrie song. “Which side are you on? It is in my view … not possible to be a candidate of corporate America, of the insurance companies or Wall Street, not take huge amounts of money from powerful special interests and then say, ‘Well, I’m going to champion the needs of the declining middle class… working class people or low-income people.’”

Sanders’ comments come as Democrats continue to reel over last week’s election results and chart the party’s path forward for the future.

House Democrats earlier this week delayed the election of their party leaders as the caucus struggled with whether to focus on appealing to the blue collar Rust Belt workers who went for Donald Trump or double down on the so-called "Obama coalition" of African-Americans, Latinos and young voters.

In the Senate, Sanders was given a new position within the Democratic caucus Wednesday focused on grassroots outreach, a nod by leaders to the progressive voters who were energized by Sanders’ presidential run. Leaders also elevated centrist Democrats from Republican-leaning states who will face challenging reelection bids in 2018 and beyond.

Sanders said he was willing to work with Trump on issues such as raising the minimum wage, protecting entitlement programs and trade – including renegotiating the North American Free Trade Agreement, or NAFTA.

The Vermonter, however, said he would not compromise on “racism, sexism, homophobia and Islamophobia.” Sanders also promised to fight Trump on climate change “tooth and nail.”

“The future of this planet is at stake and we have got to bring together people to demand that Mr. Trump listen to the scientists, not the fossil fuel industry,” he said.