Hillary Clinton told North America's Building Trades Union that she will "not let anyone undermine prevailing wage standards or project labor agreements" during the group's legislative conference Tuesday in Washington, DC.

The Democratic presidential candidate also touted her five-year, $275 billion infrastructure plan, her commitment to spurring the creation of manufacturing and clean energy jobs, and her support of apprenticeship training programs.

The crowd of union organization leaders and members booed as she addressed Sen. Ted Cruz's statements that he would support a national "right to work" law. "That’s a law that would gut unions, drive down wages and benefits, and take away even more power from working people," Clinton said to cheers from the crowd. "Right to work is wrong. It's wrong for workers, and it’s wrong for America."

NABTU, an alliance of 14 national and international unions that represent more than three million craft workers, endorsed Clinton in December, soon after she announced her transportation plan.

The crowd applauding Hillary Clinton during Tuesday's event Nan Copeland

After walking into the conference with "Respect" by Aretha Franklin playing, Clinton told the crowd, "Here’s my promise to you. If I’m fortunate enough to be your president, organized labor will always have a champion in the White House."

Clinton promised conference attendees that she "will not let anyone undermine collective bargaining rights." Clinton continued, "I will not let anyone undermine prevailing wage standards or project labor agreements. I won’t let anybody undo all the hard work and sacrifice that made careers in the building trades a ladder into a middle class life."

Project labor agreements have always been a divisive issue in the construction industry, as opponents claim that PLAs restrict competition and raise costs. A common requirement of PLAs mandates that contractors and employees must pay into union benefit plans and abide by union work rules. On the other hand, proponents of PLAs claim they are a way of controlling costs and quality on the job, and they reject the idea that they place an undue burden on nonunion contractors and employees.

Attendees holding up signs during the event Tuesday Nan Copeland

Clinton echoed a common point that union proponents cite as a reason to use organized labor, rather than an open-shop approach: "The fact is that the building trades know how to get the job done, and you do it right the first time," she said. "Too many guys get the lower bid, they have nonunion labor, and they have to fix it."

However, The Wall Street Journal reported this week that construction unions might be "losing their grip" on the private sector in New York City and other union hubs across the U.S. Developers for private city projects have said that using union labor can increase costs by 20% to 30%.

Clinton also voiced her support of union apprenticeship programs, which she said "are a form of higher education just like community college or a four-year college." Her calls for greater emphasis on training programs were similar to those from expert panelists during a HomeAdvisor forum in February, who said stronger focus on educational initiatives and training programs could make a major difference in the ongoing labor shortage plaguing the industry.

"Building a strong America requires a strong workforce," Clinton said. "There are about 1.2 million jobs right now for skilled workers. I want to fill every one of them, and I want to fill them with apprentices that have been trained by the building trades."