Trade unions are firing back against the progressive "Green New Deal" agenda and, in doing so, are revealing a split between left-leaning labor and climate advocates in the House and Senate.

The "Green New Deal" is “not achievable or realistic," read a letter from AFL-CIO energy committee heads Cecil Roberts, president of the United Mine Workers of America, and Lonnie Stephenson, president of the International Brotherhood of Electrical Workers.

"We will not accept proposals that could cause immediate harm to millions of our members and their families," the union bosses wrote.

The letter was sent last week to Rep. Alexandria Ocasio-Cortez, D-N.Y., and Ed Markey, D-Mass., the two leaders of the "Green New Deal" agenda. The letter has been trickling out on social media this week.

The Green New Deal was released by the two Democrats as a broad call to action on climate change, and has since become the policy platform for the progressive wing of the Democratic Party. It calls for radical action to reduce the threat of climate change by switching out the nation's entire energy grid to renewables in just 10 years. It offers few particulars and has raised many feasibility questions by both Democrats and Republicans.

The unions want to be part of the climate change discussion but concede that their members need assurances that the infrastructure development required to meet the nation's climate and energy goals will be part of the discussion.

The investments needed to meet the clean energy and climate goals, including increased natural gas use, must be paired with "strong labor and procurement standards to grow family-sustaining, middle-class union jobs," the letter added.

Sen. John Barrasso, R-Wyo., the chairman of the Environment and Public Works Committee, tweeted out the letter on Monday and said he agrees with the union bosses.

The @AFLCIO, which represents 12.5 million workers & includes 55 labor unions, slams the #GreenNewDeal in a letter to @SenMarkey & @AOC:



“We will not accept proposals that could cause immediate harm to millions of our members and their families.”



I agree with the AFL-CIO. pic.twitter.com/pEVhr9Ricr — Sen. John Barrasso (@SenJohnBarrasso) March 11, 2019

Markey said that he and Ocasio-Cortez will partner with the AFL-CIO but said Republicans who do not admit that climate change is real are fooling themselves. The only groups they are "in agreement with are Big Oil and the Koch brothers,” Markey tweeted.

[Opinion: The latest opponent of the Green New Deal: The AFL-CIO]