"We are writing to express our strong support for the United States remaining in the Paris Climate Agreement", it said.
A decision to drop out would put the USA at odds with almost every other nation on Earth.
USA tech entrepreneur Elon Musk has declared he will resign from Trump's advisory council if he backs out of Paris.
Musk said at the time that he would seek a consensus of fellow council members on recommendations for changes that could be suggested to Trump. Accordingly, they are increasingly investing more in green technology.
Jean-Claude Juncker said that "the Americans can't just get out of the agreement", adding that "it takes three to four years" to pull out.
What about the rest of the world?
How large are US CO2 emissions?
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Economists say that leaving the Paris deal and easing efforts to control emissions would hardly deliver a big payoff in jobs.
China and the European Union will seek on Friday to save the global pact against climate change by deepening their ties within climate and energy policies.
Former Vice President Al Gore called Trump's decision "a reckless and indefensible action" and said the move "undermines America's standing in the world".
Under Trump, who once called climate change a "hoax", Washington has resisted intense pressure from its partners to commit to respecting the global accord.
Five Nordic countries wrote a last-minute letter to Trump, saying the Paris accord was a commitment "to our children".
Since the Paris agreement doesn't pretend to obligate anyone to do anything in particular, it can best be viewed as an effort by the global climate lobby to guarantee that lavishly-funded sinecures, punctuated by vacations in desirable locations like Paris, will be available for many years to come.
Trump has already, through executive orders, moved to roll back key Obama administration policies, notably the EPA's Clean Power Plan, that comprised a key part of the U.S.'s Paris promise to reduce its emissions 26 percent to 28 percent below their 2005 levels by 2025.
"If global warming continues, there is a serious question as to whether or not mankind survives", Pallone said.
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"It is impossible for us to expect our partners to honor their commitments if the United States can not live up to our own", she said.
What impact would a USA withdrawal have?
"The U.S. has successfully bent its greenhouse gas emissions curve", Kate Larsen, of the economics research team Rhodium Group, told Christopher.
According to CNN's John D. Sutter the 2 degrees goal is incredibly consequential.
The overwhelming majority of peer-reviewed studies and climate scientists agree the planet is warming, mostly due to the burning of fossil fuels like coal and natural gas.
Elon Musk has a message for President Donald Trump: Don't leave the Paris climate agreement.
Scientists have said a USA withdrawal from the deal could speed up the effects of global climate change, leading to heat waves, floods, droughts, and more frequent violent storms.
Many economists have big doubts.
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Climate action will also continue in the USA even if Washington withdraws. If anything, we hope to see China and India stepping up the pace. "I think there will (even) be an effort on the part of many USA states and localities to help the U.S. meet its stated voluntary goal anyway", Schlosberg said.