Democratic presidential candidate Hillary Clinton is touring the US Rust Belt, seeking to shore up support from working-class voters by promising to raise wages and reject bad international trade deals.
"We are going to say 'no' to unfair trade deals, we're going to stand up to China," Clinton told unionised workers at Johnstown Wire Technologies.
"I feel strongly about this and I need your help," she added.
A pending Asia trade deal negotiated by President Barack Obama has become a flashpoint in the US presidential campaign.
Clinton has said she opposes the Trans Pacific Partnership because it does not do enough to protect US workers.
Trump has said he would rip it up and questioned whether Clinton would keep her stance if she wins the November 8 presidential election.
Leo Gerard, the president of the United Steelworkers, which represents roughly 200 of the 260 workers employed by Johnstown Wire Technologies, assured the crowd in his introduction of Clinton that Republicans have been "telling lies" about Clinton's stance on the deal.
Clinton and her running-mate Tim Kaine, a US senator from Virginia, are on a three-day tour of Pennsylvania and Ohio after becoming the first woman to accept a major US party's presidential nomination at the Democratic convention in Philadelphia on Thursday.
Pennsylvania and Ohio are two states in the US Rust Belt that are dealing with job losses caused by the decline in US manufacturing. Neither leans heavily in favour of either political party but both voted for Obama in 2008 and 2012.
Trump has zeroed in on white, working-class voters in the region as critical to his campaign and plans to visit both states early next week.