WASHINGTON – Six Democratic senators from Rust Belt states won by President-elect Donald Trump called Tuesday for a swift congressional crackdown on U.S. companies that send manufacturing jobs abroad, claiming common cause with Trump’s crusade against outsourcing.

Trump on Sunday tweeted that "any business that leaves our country for another country, fires its employees, builds a new factory or plant in the other country, and then thinks it will sell its product back into the U.S. without retribution or consequence, is WRONG!" He threatened to impose a 35 percent tariff on goods those companies seek to import.

The Democratic senators from Indiana, Ohio, Michigan, Pennsylvania and Wisconsin stopped short of calling for a protectionist tariff regime. But in a letter to congressional leaders Tuesday, they applauded "the recent attention President-elect Trump has brought to the issue of outsourcing and its impact on middle-class families" and called for legislation that would penalize companies that send jobs abroad.

Those penalties, they say, should include considering outsourcing when awarding federal contracts and potentially outsourcers from receiving tax breaks and other federal incentives, and "clawing back" those incentives if companies later ship jobs out of the country.

"The loss of manufacturing jobs in our states has contributed to the decades-long trend of the declining middle class," the letter reads. "We believe these principles-which we intend to introduce as legislation-are critical to our shared commitment to encourage companies to invest in the United States and in American workers."

The lead signer of the letter is Sen. Joe Donnelly, D-Ind., who praised the decision last month by Carrier Corp., under pressure from Trump, to reverse its decision to send hundreds of Indianapolis manufacturing jobs to Mexico. But the company is still planning to move hundreds of other jobs, and Donnelly has pushed Trump to do more

"I strongly encourage you to make it clear that efforts to ship jobs offshore to chase cheap wages will be addressed head on by the Trump Administration," he wrote in a separate letter last week. "I stand ready to assist in any way possible."

Donnelly is up for re-election in 2018 in a state where Trump won 57 percent of the vote.

Also signing the letter are Sens. Sherrod Brown, D-Ohio, Tammy Baldwin, D-Wis., Bob Casey, D-Pa., Gary Peters, D-Mich., and Debbie Stabenow, D-Mich.