Watch: Bernie Sanders Rallies With Verizon Workers on Strike in Brooklyn

Democratic presidential candidate Bernie Sanders paid an impromptu visit to a Verizon workers' picket line in Brooklyn on Wednesday after being endorsed by New York City transit workers, as he continued to try wresting labor union support from rival Hillary Clinton.

The Brooklyn-born Sanders addressed an enthusiastic crowd of striking workers from Verizon Communications Inc as "brothers and sisters" and thanked them for their courage in standing up to what he characterized as corporate greed. Nearly 40,000 Verizon employees walked off the job on Wednesday in one of the largest US strikes in recent years after contract talks hit an impasse.

"Verizon is one of the largest most profitable corporations in this country, but they refuse to sit down and negotiate a fair contract," Sanders declared. "They want to take away the health benefits that you have earned. They want to outsource decent paying jobs. They want to give their CEO $20 million dollars a year in compensation. They want to avoid paying federal income taxes. In other words, this is just another major American corporation trying to destroy the lives of working Americans."

It was a scene tailor-made for the US senator from Vermont, who has focused on income inequality in his campaign for the Democratic presidential nomination. Sanders is trying to catch up with Clinton, the front-runner, in Tuesday's primary in New York, a state both candidates have called home.

Workers cheered as Sanders criticized the mammoth communications company.

"Today you are standing up not just for justice for Verizon workers, you're standing up for millions of Americans… and you're telling corporate America that they cannot have it all," Sanders said. "You have chosen to stand up for dignity, for justice, and to take on an enormously powerful special interest."

Sanders appears around the 22:00 mark of this video.

While Sanders whipped up the crowd of hundreds in Brooklyn, Clinton's campaign issued a statement criticizing Verizon for wanting to outsource more jobs and urging the company to go back to the bargaining table.

"To preserve and grow America's middle class, we need to protect good wages and benefits, including retirement security," Clinton said. "And we should be doing all we can to keep good-paying jobs with real job security in New York."

Earlier, Clinton won the backing of a local unit, representing more than 27,000 area workers, of the International Brotherhood of Electrical Workers, one of the unions involved in the Verizon strike.

Sanders has championed the rights of working-class Americans, including a proposed $15 federal minimum wage, in daily campaign speeches targeting corporate greed.

Yet Clinton has racked up support from unions representing the majority of organized labor, a crucial base of support for the Democratic Party.

They include influential unions such as the AFSCME, a public employees union with 1.6 million members, and the Service Employees International Union, or SEIU, which has about 2 million members in a variety of professions.

In what was widely viewed as a win for Sanders, the AFL-CIO, the country's largest labor union federation, in February declined to endorse a candidate in the Democratic primary.