The U.S. officially rejoined the Paris climate change agreement on Friday as President Biden puts environmental policy at the center of his agenda and prepares to work with world leaders to cut global greenhouse gas emissions. On his first day in office last month Mr. Biden took an initial step toward rejoining the global accord, which was a signature achievement of former President Barack Obama and from which former President Donald Trump subsequently withdrew.

Under the agreement’s rules, a country can formally re-enter the pact 30 days after it gives notice to the United Nations. Friday marks the end of that 30-day period. “The work to reduce our emissions has already begun, and we will waste no time in engaging our partners around the world to build our global resilience,” Secretary of State Antony Blinken wrote on Twitter.

Mr. Trump argued that the agreement’s terms weren’t fair to the U.S. because other major emitters weren’t doing enough to cut emissions under the pact. Though Mr. Trump repeatedly said during his presidency that the U.S. was no longer a party to the agreement, the withdrawal became effective in early November 2020, near the end of his term, because it took time to formally exit the pact.

Mr. Biden has named climate change as one of four crises he hopes to address during his presidency, along with the pandemic, the ailing economy and racial injustice. The president tapped two veteran public advocates for climate action—former Secretary of State John Kerry and former Environmental Protection Agency Administrator Gina McCarthy—for senior roles in his administration.

Mr. Kerry, the U.S. special presidential envoy for climate, will take a leading role in international climate talks. Ms. McCarthy, the first-ever White House national climate adviser, will focus on domestic climate matters.

The more than 190 countries that signed the Paris agreement set a goal of containing the rise in global temperatures to no more than 2 degrees Celsius, and preferably to no more than 1.5 degrees, to limit the effects of climate change.

Under the Paris agreement, which was negotiated in 2015 and signed in 2016, each country crafted its own pledge to tackle climate change. The Obama administration in its pledge, known as a nationally determined contribution, said it would cut U.S. emissions by 26% to 28% below 2005 levels by 2025.

The Biden administration is now working on a new target. The White House has said the president is expected to announce the target at an Earth Day climate summit with world leaders set for April 22.

The president created a National Climate Task Force consisting of cabinet secretaries and other senior officials to help implement his climate agenda, which will include wide-ranging efforts across federal agencies to reduce U.S. emissions.