MONESSEN, Pa. — Donald Trump called for a new era of economic “Americanism” Tuesday, promising to restore millions of lost factory jobs by backing away from decades of U.S. policy that encouraged trade with other nations — a move that could undermine the country’s place as the dominant player in the global economy.

The speech marked a significant break from years of Republican Party advocacy for unencumbered trade between nations, and drew immediate condemnation from GOP business leaders.

In his 35-minute speech, Trump blamed former President Bill Clinton and his wife, Democratic presidential rival Hillary Clinton for the loss of millions of manufacturing jobs.

He threatened to exit the more than 2-decade-old North American Free Trade Agreement and vowed to withdraw from the Trans-Pacific Partnership, an agreement among 12 Pacific Rim nations that has yet to take effect.

At a rally later Tuesday, Trump declared that TPP had been “done and pushed by special interests who want to rape our country, just a continuing rape of our country. That’s what it is, too.”

In the speech, he pointed to China as a source of many of America’s economic woes, promising to label that country a currency manipulator and slap new tariffs on America’s leading source of imports, a decision with the potential to dramatically increase the cost of consumer goods.

“This wave of globalization has wiped out totally, totally our middle class,” Trump said, standing in front of pallets of recycled aluminum cans on a factory floor. “It doesn’t have to be this way. We can turn it around, and we can turn it around fast.”

Delivered in a hard-hit Pennsylvania steel town, the speech underscored the central message of Trump’s campaign: that policies aimed at boosting international trade — and America’s intervention in wars and disputes abroad — have weakened the country.

It’s an argument that found support among Republican primary voters, especially white, working class Americans whose wages have stagnated in recent years. Trump hopes it will yield similar success among the wider electorate that will decide the general election.

“I promise you, if I become president, we’re going to be working again. We’re going to have great jobs again,” he said. “You’re going to be so happy.”

But he drew a quick and scathing response from the U.S. Chamber of Commerce, a traditional Republican ally and leading business lobby.

“Under Trump’s trade plans, we would see higher prices, fewer jobs, a weaker economy,” the Chamber said on its Twitter feed, directing readers to a blog post that said Trump’s policies would lead to millions of job losses and a recession.

Many economists have dismissed Trump’s promise to immediately restore manufacturing jobs as dubious at best, given the impact of automation and the many years it typically takes to negotiate trade agreements.

While renegotiating tougher deals with America’s foreign trading partners might help some businesses, manufacturing as a share of total U.S. jobs has been slipping for several decades. The number of such jobs has risen slightly since the end of the Great Recession, but the introduction of robotics and access to cheaper foreign markets has reduced U.S. factory employment to a total last seen around 1941.

Indeed, the National Association of Manufacturers slammed Trump’s logic on Tuesday, with the organization’s president, Jay Timmons, writing on Twitter: “@realDonaldTrump you have it backward. Trade is GOOD for #mfg workers & #jobs. Let’s #MakeAmericaTradeAgain.”

In making his case for a new approach to trade, Trump recounted economic policies in place at the founding of the country — a time when goods traveled by horseback and schooner, the invention of the telegraph was still decades away and the advances of the Internet and broadband communication hardly imaginable.

The billionaire real estate mogul then skipped ahead to the 1990s, blaming the Clinton administration for negative impacts of globalization. He cited Bill Clinton’s support of NAFTA, which aimed to reduce barriers to trade between the U.S., Canada and Mexico, and China’s entry into the World Trade Organization.

“Throughout her career — her whole career — she has betrayed the American worker. Never forget that,” Trump said.

Clinton’s positon on trade has been a frequent attack line for Trump. She has supported some agreements, opposed others and flipped on both NAFTA and TPP, which she promoted dozens of times as secretary of state.

She now says she will back trade deals only if they fulfill a three-pronged test of creating “good jobs,” raising wages and improving national security.

But Trump, too, has evolved on the issue. In a 2005 blog post on a website affiliated with his now-defunct Trump University, the billionaire mogul argued that outsourcing isn’t always a bad thing, citing a study that found it “actually creates more jobs and increases wages, at least for IT workers.”

“We hear terrible things about outsourcing jobs_how sending work outside of our companies is contributing to the demise of American businesses. But in this instance I have to take the unpopular stance that it is not always a terrible thing,” he wrote.

The speech came as Trump, facing sliding poll numbers and a far larger Clinton campaign operation, is working to re-tool his message for the general election. In addition to a slew of new hires, he has been delivering prepared speeches aimed at calming the nerves of GOP donors and others concerned about his often combative style.

But his toned-down rhetoric didn’t last long. At a rally Tuesday evening in St. Clairsville, Ohio, in addition to comparing the TPP to rape, Trump reiterated his call for the return of waterboarding and other harsh interrogation techniques in the fight against Islamic State militants, declaring, “you have to fight fire with fire.”

The comment drew cheers and chants of “USA! USA!” from the crowd.

Lerer reported from Washington. Associated Press writers Ken Thomas and Josh Boak in Washington contributed to this report.