The Paris climate agreement took force on Friday, starting an ambitious, though largely non-binding, worldwide effort to fight climate change.

The pact is the first international accord of its kind, putting nearly 200 nations on the same footing with the same expectations for developed and developing nations to do their parts to reduce greenhouse gas emissions.

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Its entry into force represents a major victory for President Obama.

He dedicated a large portion of his diplomatic energy in his second term to securing a worldwide climate deal that would have an impact without requiring ratification in the Senate.

“Reaching the Paris agreement in December of last year was clearly a watershed moment for the international community,” John Morton, director for climate and energy at the White House National Security Council, told reporters Thursday.

Morton said the agreement is taking effect “much, much faster, years faster, than most people expected. And with that entry into force, that puts us on a much accelerated path toward implementation of that goals that we laid out in Paris a year ago.”

The agreement is taking effect because the European Union, Canada and Nepal ratified it last month, pushing it across the final threshold.

The pact consists of individual pledges that each nation made to limit or cut greenhouse gas emissions. The United States’s pledge is to cut 26 percent to 28 percent of emissions by 2025.

But those cuts are not binding under international law, which means the Senate does not have to vote on the accord. Congressional Republicans have blasted the pact as a blatant end-run around the Senate’s powers.

Republicans have tried to undermine Obama by convincing leaders of other nations that the United States’s pledge won’t stand.

Sen. James Inhofe James (Jim) Mountain InhofeChamber of Commerce endorses McSally for reelection Overnight Defense: Top admiral says 'no condition' where US should conduct nuclear test 'at this time' | Intelligence chief says Congress will get some in-person election security briefings Top admiral: 'No condition' where US should conduct nuclear test 'at this time' MORE (R-Okla.) and 13 colleagues argued in a letter Thursday to Secretary of State John Kerry John Forbes KerryThe Memo: Warning signs flash for Trump on debates Divided country, divided church TV ads favored Biden 2-1 in past month MORE that Obama’s climate policies and his ratification of the pact are on shaky legal footing and likely to be struck down in the courts or Congress.

“We are concerned the administration has not been forthright in acknowledging the limitations of the president’s domestic climate actions, primarily the Clean Power Plan, and the pathway the administration has taken to join the Agreement,” they wrote. “We urge you to be candid with parties to the Agreement to preserve the diplomatic credibility of the United States.”

The lack of Senate ratification for the pact means that a future administration, such as that of Republican presidential nominee Donald Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE, would be under no formal obligation to abide by Obama’s pledge.

Trump, who has said climate change is a hoax, is pledging to “cancel” the Paris agreement and pull the United States out of it. It would take four years to formally exit the pact, but Trump has also promised to undo all of Obama’s executive actions to fight climate change, which would most likely prevent the U.S. from reaching its goal.

Rep. Kevin Cramer (R-N.D.), a surrogate for Trump, said recently that the Paris pact puts U.S. interests secondary to those of other nations.

“The acquiescence of American interests to global interests has been going on way too long. And the Paris climate accord is one more bad trade deal,” he said, putting it on par with other international agreements Trump wants to stop or renegotiate.

Cramer said Trump might submit the agreement for Senate ratification, which would certainly fail, in order to show the world that the U.S. opposes it.

Democratic nominee Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE has applauded the Paris agreement and taken some credit for it from her work as secretary of State. In 2009, she and Obama, at a Copenhagen climate conference, pressured China to cooperate with the U.S. on climate change.

Despite the uncertainty surrounding the election, supporters of the pact celebrated the deal taking force, calling it a milestone.

“It’s a historic victory for the kind of global cooperation required to leave our children a brighter, more hopeful tomorrow,” said Rhea Suh, president of the NRDC Action Fund, the political arm of the Natural Resources Defense Council, in a statement.

“The entry into force of the Paris Agreement means that the world now has a legal mandate to build a zero carbon future,” Philippe Joubert, chairman of the Europe-based Prince of Wales’s Corporate Leaders Group, said in a statement. “By ratifying the agreement with unprecedented speed, governments have shown that they understand the urgency of the climate challenge.”

Representatives of the parties to the Paris agreement are meeting Monday in Marrakech, Morocco, to discuss the next steps for the pact, including how to track countries’ progress and other implementation questions.