Former President Barack Obama said on Thursday that the cities and businesses of the United States should step up to reduce greenhouse gases after President Donald Trump announced that America would withdraw from the Paris climate change accord.

The mayor of Pittsburgh, pushing back on Trump’s statement that he was elected to represent the citizens of that former steel-making giant rather than those of Paris, condemned the withdrawal.

Tech entrepreneur Elon Musk immediately announced he will quit presidential advisory councils. Disney CEO Bob Iger said he was out, too. General Electric Chairman and CEO Jeff Immelt said "Climate change is real. Industry must now lead and not depend on government."

Am departing presidential councils. Climate change is real. Leaving Paris is not good for America or the world. — Elon Musk (@elonmusk) June 1, 2017

"The United States joins Syria, Nicaragua & Russia in deciding not to participate with world's Paris Agreement. It's now up to cities to lead," Pittsburgh Mayor Bill Peduto, a Democrat, said on Twitter.

Trump said at an announcement at the Rose Garden on Thursday that the United States would withdraw from the international agreement negotiated under Obama, citing a desire to protect American jobs and fuel what he has claimed would be three percent economic growth.

Related: What It Means That Trump Is Leaving the Paris Climate Agreement

Because Obama didn’t ask the Senate for approval of the Paris accord, Trump can act unilaterally without the consent of Congress. Democrats, however, could slow down any action on the floor in retaliation of the decision and tie any pending nominations to the issue, actions that won’t change the outcome but frustrate Republicans and the White House.

Obama said in a statement that a withdrawal means an abdication of American leadership.

"The nations that remain in the Paris Agreement will be the nations that reap the benefits in jobs and industries created. I believe the United States of America should be at the front of the pack," Obama said in the statement.

"But even in the absence of American leadership; even as this Administration joins a small handful of nations that reject the future; I’m confident that our states, cities, and businesses will step up and do even more to lead the way, and help protect for future generations the one planet we’ve got,” Obama said.

Related: California and Other States Step Into the Climate Policy Void

Reaction on Capitol Hill was mostly partisan, with Republicans standing by the president’s decision, praising the U.S.'s withdrawal as good for the economy. "President Trump has once again put families and jobs ahead of left-wing ideology and should be commended for his action,” Republican Senate Majority Leader Mitch McConnell said.

But some Republicans in Congress opposed Trump’s move. Sen. Susan Collins of Maine said on Twitter: "Climate change requires a global approach. I'm disappointed in the President's decision to withdraw from the Paris Agreement."

Republican Rep. Carlos Curbelo of Florida, who is expected to have a tough re-election in his swing district in south Florida, lobbed a series of tweets in opposition.

Something's not right when @POTUS is putting our country on a list with bad hombres Bashar al Assad of Syria & Daniel Ortega of Nicaragua — Carlos Curbelo (@carloslcurbelo) June 1, 2017

Trump had pledged on the campaign trail to withdraw from the 2015 Paris climate accord, which is a non-binding agreement that asks that all signing countries — rich and poor — take concrete steps to reduce their carbon emissions in the face of climate change.

The Obama administration pledged a 26 to 28 percent cut in U.S. emissions, which Republicans have criticized for potentially having a negative impact on the American economy and its energy sector.

Former Sectary of State John Kerry said on MSNBC that the move to withdraw from the Paris deal was "an extraordinary abdication of American leadership."

He noted that the program was voluntary, and the United States was not forced to do anything under the accord.

"It was a voluntary program. We designed the program," Kerry said. "The president was not truthful with the American people today, and the president who talked about putting 'America first' has now put America last."

Withdrawing from the climate deal could take three years, European Commission President Jean-Claude Juncker said this week.

And French President Emmanuel Macron, German Chancellor Angela Merkel and Italian Premier Paolo Gentiloni said in a joint statement Thursday that they take note "with regret" the U.S. decision to pull out of the 2015 agreement.

The three leaders say they regard the accord as "a cornerstone in the cooperation between our countries, for effectively and timely tackling climate change."

They added that the course charted by the accord is "irreversible and we firmly believe that the Paris Agreement cannot be renegotiated."

Macron, Merkel and Gentiloni say they remain committed to the deal and will "step up efforts" to support the poorest and most threatened nations.

Decision to withdraw from the #ParisAgreeement was wrong for our planet. Apple is committed to fight climate change and we will never waver. — Tim Cook (@tim_cook) June 2, 2017

U.N. spokesman Stephane Dujarric called Trump's decision a "major disappointment for global efforts to reduce greenhouse gas emissions and promote global security."

Canadian Prime Minister Justin Trudeau said on Thursday "We are deeply disappointed that the United States federal government has decided to withdraw from the Paris Agreement" and said Canada is committed to fighting climate change.

Related: Fact Checking Trump's Paris Agreement Speech

Trump on Thursday left open the possibility of renegotiating what he called a better deal that would put American taxpayers first, and suggested the climate deal was a ruse that put the United States at a competitive disadvantage.

"The agreement is a massive redistribution of United States wealth to other countries," Trump said.

Former President Bill Clinton said on Twitter: "Walking away from Paris treaty is a mistake. Climate change is real. We owe our children more. Protecting our future also creates more jobs."

And Goldman Sachs CEO Lloyd Blankfein said in his first tweet from a verified account that "Today's decision is a setback for the environment and for the U.S.'s leadership position in the world," adding the hashtag #ParisAgreement.

Today's decision is a setback for the environment and for the U.S.'s leadership position in the world. #ParisAgreement — Lloyd Blankfein (@lloydblankfein) June 1, 2017

The governors of New York, California, and Washington state said in a statement that they would form a "United States Climate Alliance" which they called "a coalition that will convene U.S. states committed to upholding the Paris Climate Agreement and taking aggressive action on climate change."

Related: Why Trump Is Seeing Red About the 'Green Climate Fund'

A speaker at a protest near the White House called the move "treason" and the crowd chanted "lock him up," a play off of Trump supporters’ chants targeting Hillary Clinton during the presidential campaign.

Trump's announced withdrawal from the climate deal was not unexpected. On Wednesday in a tweet in which Trump said he would announce his decision on Thursday, the president ended with his signature phrase: "Make America great again."