Washington (CNN) In light of President Donald Trump's decision to withdraw the US from the Paris Climate Accord, dozens of governors and mayors across the country are pledging to uphold the green fight within their own borders.

A group of 83 "climate mayors" issued a statement following Trump's announcement pledging to "adopt, honor and uphold the commitments to the goals enshrined in the Paris Agreement."

New York's Bill de Blasio and Los Angeles' Eric Garcetti were among the those in the group saying, "The world cannot wait -- and neither will we."

The mayors promised to increase investment in renewable energy and energy efficiency, buy and create more demand for electric vehicles, and increase their efforts "to cut greenhouse gas emissions, create a clean energy economy, and stand for environmental justice."

The White House says if states and cities want to go it alone, that's OK.

"If a mayor or a governor wants to enact a policy that's, on a range of issues, they're accountable to their own voters and that's what they should do," White House press secretary Sean Spicer told reporters Friday. "We believe in states' rights and so if a locality, a municipality or a state wants to enact a policy that their voters or their constituents believe in than that's, that's what they should do."

The governors from New York, California and Washington banded together Thursday to form the US Climate Alliance, an organization similarly vowing to uphold the main tenants of the Paris Climate Accord, including reducing carbon emissions by 26% to 28% from 2005 levels by 2025.

"This is an insane move by this president -- the world depends on a sustainable future," California Gov. Jerry Brown said in a call to reporters. "It's tragic, but out of that tragedy I believe the rest of the world will mobilize, will galvanize our efforts."

The three governors plan to meet the goal through state executive orders . In New York's executive order, Gov. Andrew Cuomo called Trump's decision to pull out from the Paris agreement an "abdication of leadership on climate change that threatens the environmental and economic health of all New Yorkers."

JUST WATCHED Macron to US: Make our planet great again Replay More Videos ... MUST WATCH Macron to US: Make our planet great again 01:01

All three states, however, are already leading the pack when it comes to cutting emissions and working against climate change. For example, New York state has in place a State Energy plan that includes reducing green house gas emissions by 40% from 1990 levels by 2030 and a commitment to source 50% of the state's electricity from renewable by the same year.

Former New York Mayor Michael Bloomberg's philanthropic group pledged $15 million Thursday to "fill the gap left by the US government backing out of its commitments."

Bloomberg was appointed by former President Barack Obama to be a special UN Envoy for mayors and local leaders assigned to help them meet the goals signed under the Paris Accord. The money will fund the UN's climate secretariat, which will lose money under Trump.

In a conference call Friday, members of the United Conference of Mayors also voiced their commitment to do whatever it takes to prove the US' commitment to combating climate change.

"We will do what we have to do on our own to protect jobs, protect national security and protect the environment. All things that we think go hand in hand," said New Orleans Mayor Mitch Landrieu. "This is not the first time we've had to work without the federal government -- we're ready to take the lead on this issue and other issues that affect the country."

Gearing up for Trump's decision, Reps. Earl Blumenauer of Oregon, Jared Huffman of California, and Suzan DelBene of Washington, along with 18 other West Coast members of Congress, sent a letter Wednesday urging governors in their states to form a "green wall" to maintain climate leadership in the country.

"While President Trump continues to ignore reality, we are particularly grateful for your efforts. In order to send a signal to the international community, and to uphold our obligations to current and future generations, we encourage you to continue to aggressively address the threat of climate change and abide by this international effort," the lawmakers wrote in the letter.

They added: "The Paris Agreement calls for significant reductions in greenhouse gas emissions, and if Donald Trump's administration won't lead, our states must."

Will it work?

However, it remains unclear just how efficient cross-city and cross-state climate pacts will ultimately be in the face of a federal government determined to loosen restrictions on emissions and ramp up coal and natural gas production. While states can determine their own energy goals, they cannot effect other areas of the country whose economy is heavily reliant on fossil fuel production, and who aim to benefit from the White House's recent change of course.

Local leaders acknowledge how much harder it will be to work not just without, but potentially against, the federal government in order to maintain their lower emissions and renewable energy goals. However, they also refuse to look at the alternative -- an America where no leaders are fighting back against global warming and that offers no hope to cities and countries internationally who still look to the US for guidance.

"I want to give people hope, but not false hope on this process." said Phoenix Mayor Greg Stanton. "It's going to be a lot harder for the US to meet its commitments on the Paris Accord without the president being on board. The mayors across the US will do everything in our power, and step up our game in ways you've never seen. We need to give people hope across the globe and stand up for our communities."