President-elect Donald Trump most recent opponent is an Indianapolis union leader, as the two have exchanged a back-and-forth this week following Trump's initial announcement of a large tax-break deal with Carrier, an air conditioning manufacturer, that he claimed would keep 1,100 jobs at the Indiana plant.

That claim proved untrue. Chuck Jones, president of the local United Steelworkers union group that represents the plant employees, later told the Washington Post that Trump "lied his ass off."

"What nobody’s mentioning is 550 people are losing their jobs," Jones later said on CNN. Jones also stated that hundreds of other jobs were heading to Mexico.

The CEO of Carrier's parent company meanwhile, confirmed on CNBC that the company still planned to shutter one of its Indiana factories and send other jobs to Mexico.

Trump responded by attacking Jones on Twitter, saying he's done a "terrible job" and disparaged the union.

This is not Trump's first run-in with organized labor. His hotels and properties have had their fair share of disagreements with unions, especially a Las Vegas property that has been the subject of many National Labor Relations Board complaints, Newsweek reported in June.

Meanwhile, labor leaders have long expressed their reservations about Trump. Richard Trumka, president of the American Federation of Labor and Congress of Industrial Organizations (AFL-CIO), said during the campaign that Trump was anti-union and shed "crocodile tears about lost jobs and shuttered factories."

"Trump embodies everything that is wrong with our current trade policy. He has consistently sent American jobs overseas to line his own pockets," Trumka said in a June speech.

Democratic presidential nominee Hillary Clinton earned the endorsement of the AFL-CIO and the United Steelworkers. Attacking a union leader might not help Trump's standing with labor. Jones said he has received phone calls threatening him and his family.

"He needs to worry about getting his Cabinet filled," Jones said to the Post. "And leave me the hell alone."