The UN chief's statement did not mention Joe Biden and Kamala Harris by name.
Top United Nations leadership hailed the election of Democrat Kamala Harris as America's first Black and South Asian-descent woman Vice President, applauding her for breaking "yet another ceiling" and describing it as a "milestone for gender equality".
UN Secretary-General Antonio Guterres is always pleased and "always welcomes any instance where women leaders... where a woman gets to break" a new or "yet another ceiling," his spokesman phane Dujarric said at the daily press briefing Monday when asked about Kamala Harris being elected as America's first woman vice president.
In a tweet, President of the 75th session of the United Nations General Assembly Volkan Bozkir extended "warmest congratulations" to President-elect Joe Biden, 77, and Kamala Harris, 56.
He said Joe Biden has a "long history of supporting" the United Nations and Kamala Harris's historic election as America's first woman vice-president is a milestone for gender equality.
"I look forward to deepening UN-US ties & working together towards a safer & more prosperous world," Bozkir said in the tweet.
Kamala Harris's election as America's next Vice President is groundbreaking as she brings to the office a litany of firsts - she will be the first woman, the first Black woman, the first woman of Indian descent and the first daughter of immigrants to be sworn in as Vice President.
Head of UN Women Phumzile Mlambo Ngcuka, described the prospect of having the first-ever woman as vice president as "a hugely uplifting moment" for women and girls the world over, "especially for women of colour".
In a statement, Guterres congratulated the American people for a vibrant exercise of democracy in their country's elections last week. "He congratulates the President-elect and Vice President-elect and reaffirms that the partnership between the United States and the United Nations is an essential pillar of the international cooperation needed to address the dramatic challenges facing the world today," the statement issued by the UN spokesperson said.
The UN chief's statement did not mention Joe Biden and Kamala Harris by name, using just the terms President-elect and Vice President-elect. When asked at the press briefing about the statement not mentioning their names, phane Dujarric said Guterres is "talking about Joe Biden and Kamala Harris."
The comments by Guterres and Bozkir on Monday were the first reactions from the world organisation's top leadership to the election victory of the next leaders of the organisation's host country, coming two days after Joe Biden and Kamala Harris were declared winners of a bitterly-fought presidential election, which outgoing President Donald Trump has still not conceded despite failing to get 270 electoral college votes required to win his re-election.
Trump secured 214 electoral college votes while Joe Biden won with 279 votes.
Director-General of the UN Educational, Scientific and Cultural Organisation (UNESCO) Audrey Azoulay said in a tweet that the "global challenges of today call for a renewed commitment from the United States" for the common good that the pillars of science, education, and culture represent.
She also noted that she was "very happy to see a teacher" moving into the top job at the White House, in the form of Joe Biden's wife Jill Biden, who has indicated that as First Lady, she will continue working fulltime.
Head of the UN refugee agency UNHCR Filippo Grandi said in a tweet that "US leadership is more crucial than ever for the world's most vulnerable."
He warmly congratulated the pair and said the agency was looking forward to working with the new administration "on global and domestic refugee issues."
António Vitorino, the Director-General of the International Organisation for Migration (IOM) said on Twitter that the UN migration agency was looking forward to working with the new administration "on managing migration for the benefit of all."
Earlier, head of World Health Organisation Tedros Adhanom Ghebreyesus congratulated Joe Biden and Harris, saying "we look forward to working with their administration very closely."
After Trump made the decision to withdraw the US from WHO earlier this year in response to alleged missteps over the early course of the coronavirus pandemic, the president-elect has repeatedly vowed to rejoin the organization.
Joe Biden over the weekend also tweeted out that his administration would be rejoining the Paris Climate deal on day one of the new administration.
On a question of whether the Secretary-General expects the US to re-enter the Paris Climate Agreement, from which the Trump administration withdrew, phane Dujarric said the Un chief's strong position in defence of the Paris Climate Agreement has never wavered and Washington and the UN have a "critical relationship" as "we face many problems throughout the world."
Phane Dujarric added that there's been no direct contact yet between Joe Biden and Guterres since the election results were out.