WASHINGTON — Just a day after giving his full support to Hillary Clinton, Sen. Bernie Sanders pledged Wednesday that he will do everything he can to prevent the presumptive Republican nominee, Donald Trump, from becoming the next president.

“His slander, his lies about the Latino community are unacceptable,” said Sanders amid fervent acclamations from Latinos at the League of United Latin American Citizens convention. “The job of the next president in this very difficult time is to bring the American people together, not separate us.”

Turning out a strong Hispanic vote is key to any Democratic scenario for victory in November.

Stressing that the strength of the country is its diversity, Sanders, in a fiery speech, urged Latinos to come together to fight against “demagogues.”

In his talk to several hundred at the boisterous event, the senator from Vermont talked about what he sees as a pressing need for Congress to pass comprehensive immigration reform. Clinton’s campaign and his campaign are working hand in hand to offer a pathway to citizenship for 11 million undocumented people, he said.

The idea is to build on President Barack Obama’s executive actions to spare from deportation the parents of children who came to the U.S. at a young age and attend school here – so-called dreamers. However, Obama’s plan has been blocked in court and Trump has vowed to build a wall along the Mexican border to stop illegal immigrants from entering the U.S.

“We don’t need Donald Trump’s wall and barbed wire,” Sanders said. “We need to fix our broken immigration system.”

Trump, a billionaire real estate developer who has never held public office, has denied any racist motives and says Americans must be protected from undocumented individuals with criminal backgrounds.

But Sanders was on the attack. “Republicans in Congress continued to obstruct, obstruct and obstruct,” he said. “The next president of the United States has got to use all of the executive powers of the presidency to extend legal protections to everyone.”

With the theme, “United for a Diverse America,” the 87th annual LULAC National Convention aimed to encourage Latino citizens to register and vote on Election Day in November. Brent Wilkes, executive director of the national civil rights organization, said votes of Hispanics will be decisive in the presidential election.

“The attitude that he [Trump] is advocating about our community is absolutely outrageous,” Wilkes said. “He’s trying to pit the white community against the Latino community of the United States. It’s disgusting and it’s something that we certainly are getting fired up about.”

Wilkes said that Trump’s rhetoric is what will galvanize the Latino population to vote. However, Latinos have not always come out in large numbers in past elections.

“We’re gonna respond,” Wilkes vowed. “It’s gonna be a big response.”

Hilary Clinton, who hopes to attract millions of Latino votes, will speak to the convention on Thursday. Housing and Urban Development Secretary Julian Castro is expected to speak.