NEW YORK - Antonio Guterres was sworn in Friday for a second 5-year term as U.N. Secretary-General after the General Assembly approved it by acclamation.

"I am acutely aware of the immense responsibilities you are entrusting me with at such a critical moment in history - dare I say, at the cusp of a new era," Guterres told the assembly after taking his oath of office. "We are truly at a crossroads, with consequential choices before us."

He pledged to serve all member states equally with no agenda, and to work to sow trust between and among nations.

"I will also seek to inspire hope that we can turn things around, that the impossible is possible," he said. "The attitude is never to give up."

On June 8, the powerful U.N. Security Council gave its blessing to his second term.

"The members of the Security Council expressed their unconditional support for Mr. Antonio Guterres," Estonian Ambassador Sven Jurgenson, Security Council president this month, told the General Assembly. "In the council's view, Antonio Guterres corresponds to the highest standards of efficiency, competence and integrity, and a firm commitment to the purposes and principles of the Charter of the United Nations."

The 15-nation council's approval is critical, because any of the five permanent members (Britain, China, France, Russia and the United States) can block the nomination with their veto. That happened in 1996, when the United States prevented the re-appointment of Boutros Boutros-Ghali.

"The United Nations is confronted with historic challenges, including a global pandemic, the effects of the climate crisis, mass hunger and migration, human rights abuses, and humanitarian crises," U.S. Ambassador Linda Thomas-Greenfield said in a statement congratulating Guterres on his reappointment. "Secretary-General Guterres has demonstrated a commitment to advancing our collective action to address these challenges, as well as the mission of the United Nations."

Guterres, 72, ran unchallenged. His candidacy was supported by the government in his native Portugal and President Marcelo Rebelo de Sousa was present at his swearing-in.

A former Portuguese prime minister, Guterres took over the U.N. reins in 2017, three weeks before Donald Trump was inaugurated as U.S. president. Guterres spent much of his first term trying not to run afoul of the administration and ending up in the former president's Twitter feed.

Preventing conflicts and combatting climate change have been two of Guterres' signature issues. Then along came COVID-19. The U.N. chief has tried to turn a global catastrophe into an opportunity for "building back better."

Rights groups have criticized Guterres for not being more vocal about human rights abuses by China, Russia, the United States and their allies.

"With his reelection behind him, the secretary-general should start calling out all governments that commit human rights abuses, including those that are powerful and protected," said Louis Charbonneau, U.N. director at Human Rights Watch.

U.N. officials say such criticism is unfair and that Guterres does raise abuses both publicly and with leaders in private.

The U.N. chief also will have no shortage of conflicts and humanitarian crises to deal with in a second term. Most, if not all of the conflicts that were in progress when he came to office five years ago are still unresolved today, and several new ones, including in Myanmar and Ethiopia, present fresh threats to international peace and security.

"It's not for want of trying," a senior U.N. official said of Guterres' conflict prevention and resolution efforts. "He's been very much engaged on all fronts."