US President Joe Biden signed a series of executive orders to launch his administration Wednesday, including a decision to rejoin the Paris climate accord and a mask mandate for all federal buildings.

The orders included keeping the United States in the World Health Organization, ending the ban on entries from mostly Muslim-majority countries, bolstering environmental protections and strengthening the fight against Covid-19.

Also among the directives was a halt to the construction of the wall on the US-Mexico border, and efforts to expand diversity and equality for minority groups in the federal government.

The orders were aimed at reversing decisions by his predecessor Donald Trump and setting a clear policy path for Biden's new administration, just hours after he was sworn in as president.

"Some of the things we are going to be doing are going to be bold," he said in the Oval Office.

"We are going to combat climate change in a way we have not done so far," Biden said of returning to the Paris agreement, a treaty signed by most nations in 2016 to limit global warming.

He said his actions on the Covid-19 pandemic, which has claimed 400,000 American lives, would help change the course of the crisis.

His return to the Paris Agreement, which the United States joined Barack Obama was president and Biden vice president, was lauded by other leaders. "Welcome back," said French President Emmanuel Macron.

"We are together. We will be stronger to face the challenges of our time. Stronger to build our future. Stronger to protect our planet."

UN Secretary-General Antonio Guterres also welcomed the move, saying it was a large step for the leading producers of global carbon pollution. "But there is a very long way to go," he said in a statement.

"We look forward to the leadership of United States in accelerating global efforts towards net zero" emissions, he said, calling for "ambitious" new targets for 2030 and expanded climate finance.

Biden's climate czar John Kerry hailed the move as a boon for "America's credibility and commitment — setting a floor, not a ceiling, for our climate leadership."

Mexico's welcome

In reaction, Mexico hailed US President Joe Biden's order to halt the construction of Donald Trump's wall along the US-Mexican border, as well as his other immigration-linked reforms.

"Mexico welcomes the end of the construction of the wall, the immigration initiative in favor of DACA and a path to dual citizenship," Foreign Minister Marcelo Ebrard wrote on Twitter.

He was referring to the Deferred Action for Childhood Arrivals program to regularize the immigration status of young people who arrived illegally as children, which Trump tried to shut down.

The Republican sparked anger during his 2016 election campaign when he branded Mexican migrants "rapists" and drug dealers, and vowed to build a wall across the southern US border.

The order to stop work on the hulking steel fence was one of Biden's first acts after he was sworn in on Wednesday.

The Democrat also plans to send a bill to Congress to revamp immigration policies and give millions of undocumented migrants living inside the country a path to citizenship, according to his aides.

Mexican President Andres Manuel Lopez Obrador was one of the last high-profile leaders to congratulate Biden on his election victory, saying he wanted to wait until legal disputes were resolved in Trump's quest to have the result overturned.

Relations between the neighbors have also been strained over the case of a former Mexican defense minister accused by the US of cartel ties.

Lopez Obrador on Wednesday wished Biden success ahead of his inauguration and said that he agreed with his policy priorities, including on the migration issue.

World leaders congratulate Biden

World leaders said they were looking forward to working with Joe Biden, the Democrat sworn in as US president on Wednesday after four turbulent years under Donald Trump.

- European Union -

Charles Michel, president of the European Council, tweeted congratulations to Biden and Vice President Kamala Harris, adding: "It's time to bring back conviction & common sense and rejuvenate our EU-US relationship."

European Commission President Ursula von der Leyen said: "Europe is ready for a fresh start."

- Iran -

President Hassan Rouhani hailed the departure of "tyrant" Trump, Tehran having repeatedly called on Washington to lift sanctions imposed over its nuclear drive.

"We expect (the Biden administration) to return to law and to commitments, and try in the next four years, if they can, to remove the stains of the past four years," said Rouhani.

Biden's administration wants the United States back in the landmark Iran nuclear accord, from which Trump withdrew, provided Tehran returns to strict compliance.

- Israel -

Prime Minister Benjamin Netanyahu urged Biden to strengthen the long-standing alliance between the two countries.

"I look forward to working with you to further strengthen the US-Israel alliance, to continue expanding peace between Israel and the Arab world and to confront common challenges, chief among them the threat posed by Iran," Netanyahu said in a video. 

- NATO -

"The bond between North America and Europe is the bedrock of our security, and a strong NATO is good for both North America and Europe," said NATO General Secretary Jens Stoltenberg.

"NATO Allies need to stand together to address the security consequences of the rise of China, the threat of terrorism, including in Afghanistan and Iraq, and a more assertive Russia."

- The Vatican -

Pope Francis urged Biden to promote "reconciliation and peace" around the world. 

"At a time when the grave crises facing our human family call for far-sighted and united responses, I pray that your decisions will be guided by a concern for building a society marked by authentic justice and freedom," the pope said.

- Russia -

Kremlin spokesman Dmitry Peskov said Russia would seek "good relations with the United States", while a foreign ministry statement said they expected a "more constructive" approach to upcoming arms control talks.

The US and Russia are to discuss extending the landmark 2010 New START nuclear weapons accord shortly after Biden's swearing in.

- Germany -

Chancellor Angela Merkel said she was looking forward to a "new chapter of German-American friendship and cooperation".

"Warmest congratulations on your inauguration, @POTUS Joe Biden and @VP Kamala Harris -- a true celebration of American democracy," Merkel was quoted as saying in a tweet posted by her spokesman Steffen Seibert.

- France -

French President Emmanuel Macron tweeted: "Best wishes on this most significant day for the American people! 

"We are together. We will be stronger to face the challenges of our time. Stronger to build our future. Stronger to protect our planet. Welcome back to the Paris Agreement!," Macron wrote in English.

He was referring to the 2015 international accord committing all nations to cut carbon emissions to limit global warming, but which the United States under Trump formally quit in November last year.

- Britain -

Prime Minister Boris Johnson, who has faced criticism over his close relationship with Trump, said he was looking forward to "working closely" with Biden.

"In our fight against Covid and across climate change, defence, security and in promoting and defending democracy, our goals are the same and our nations will work hand in hand to achieve them," he said.

Queen Elizabeth II sent a private message to Biden before he was sworn in, Buckingham Palace said, without revealing the contents of the message.

- Ireland -

"Today a true friend of Ireland @JoeBiden became the 46th President of the USA," Prime Minister Micheal Martin wrote on Twitter.

"It is a day of history and hope and I look forward to forging ever closer ties between our two great nations."

- Canada -

"Our two countries are more than neighbours -- we are close friends, partners, and allies," Prime Minister Justin Trudeau said, pledging Canada's cooperation in fighting the coronavirus pandemic, for climate action and for a sustainable economic recovery.

- India -

Indian Prime Minister Narendra Modi tweeted: "My warmest congratulations to @JoeBiden on his assumption of office as President of the United States of America. I look forward to working with him to strengthen India-US strategic partnership."

- Japan -

Japan's Prime Minister Yoshihide Suga tweeted his congratulations, adding "I look forward to working with you and your team to reinforce our alliance and to realize a Free and Open Indo-Pacific."

- South Korea -

South Korean President Moon Jae-in hailed Biden's inauguration, saying: "America is back. America's new beginning will make democracy even greater. Together with the Korean people, I stand by your journey toward 'America United'."

- Gulf states -

The leaders of Kuwait, Qatar, Bahrain, Saudi Arabia and the United Arab Emirates all sent messages of congratulations.

- Palestinian president -

Palestinian president Mahmud Abbas said he was "impatient" to work together with Biden "for peace and stability in the region and in the world".