WASHINGTON (Reuters) - Labor unions say they are withholding support for a Green New Deal unveiled by Democrats last week to transition the American economy away from fossil fuels, arguing the loosely-defined plan could kill jobs if its architects aren’t careful.

FILE PHOTO: U.S. Representative Alexandria Ocasio-Cortez (D-NY) and Senator Ed Markey (D-MA) hold a news conference for their proposed "Green New Deal" to achieve net-zero greenhouse gas emissions in 10 years, at the U.S. Capitol in Washington, U.S. February 7, 2019. REUTERS/Jonathan Ernst

The cool response from unions underscores the challenge facing Democratic presidential hopefuls who support aggressive action on climate change but must also win back the blue-collar voters that swept President Donald Trump to victory in 2016.

The Green New Deal is a non-binding Congressional resolution introduced by Representative Alexandria Ocasio-Cortez and Senator Edward Markey that would legislate government-led investment in clean energy infrastructure with the goal of making America carbon neutral within a decade.

Democratic presidential hopeful Senators Kamala Harris, Kirsten Gillibrand, Cory Booker and Elizabeth Warren have already thrown their support behind it.

The resolution’s backers say the plan - once fully sketched out in the legislation - would create jobs in much the same way as President Franklin Roosevelt’s New Deal of the 1930s by putting Americans to work on transformative government-led projects.

It also calls for a “just transition” for current fossil fuel workers - from coal miners to pipeline workers - through guarantees of healthcare, jobs, and job training.

Union officials told Reuters they were skeptical.

“We will never settle for ‘just transition’ language as a solution to the job losses that will surely come from some of the policies in the resolution,” said Yvette Pena O’Sullivan, executive director of the Laborers’ International Union of North America (LIUNA), whose members work in construction and other industries.

Phil Smith, a spokesman for the United Mine Workers (UMWA), which represents workers in the coal industry, echoed the concerns.

“We’ve heard words like ‘just transition’ before, but what does that really mean? Our members are worried about putting food on the table,” he said.

LIUNA and UMWA said they were not contacted for input on the resolution before it was released.

Sean McGarvey, president of the North America’s Building Trades Unions, representing construction workers across all sectors including energy, said his staff had been contacted by Markey’s office about the Green New Deal, but said his members are skeptical of “green job” promises.

Members “working in the oil and gas sector can make a middle-class living, whereas renewable energy firms have been less generous,” he said at a pipeline safety event last week.

APPALACHIAN BACKLASH

Democrats backing the resolution are seeking to highlight the contrast in their position with the Trump administration’s vocal support for drilling and mining and its skepticism about the causes and impacts of global warming.

Trump’s approach was warmly received in 2016 in parts of Appalachia and the Rust Belt, which have been suffering from manufacturing and mining jobs losses.

Trump’s Democratic challenger Hillary Clinton struggled to sell her clean energy agenda in those regions, and suffered politically after saying her policies would “put a lot of coal miners and coal companies out of business.”

The Sunrise Movement, a youth organization backing the Green New Deal, plans to launch a multi-state campaign in March to drum up support, featuring stops in Michigan, Kentucky and Pennsylvania.

“A lot of places struggling with joblessness are fossil fuel dependent places that suffer from poor air and water quality. Guaranteeing the right of clean air, water and jobs is something we think a lot of people can get behind,” said Stephen O’Hanlon, a spokesman for the group.

Unions have expressed support in the past for more moderate approaches to addressing climate change, including cap-and-trade systems to curb carbon dioxide emissions.

Ocasio-Cortez and Markey’s offices did not respond to a request for comment.