World leaders congratulated President Joe Biden on his inauguration Wednesday while expressing optimism about strong relations between the U.S. and their countries.

Some leaders, meanwhile, couldn’t resist taking digs at outgoing President Donald Trump.

"Once again, after four long years, Europe has a friend in the White House," European Commission President Ursula von der Leyen said Wednesday in the European Parliament in Brussels, Belgium. 

"This new dawn in America is the moment we've been waiting for so long. Europe is ready for a new start with our oldest and most trusted partner,” she added.

German President Frank Walter Steinmeier said in a statement: "In the United States, [democracy] held up against a lot of pressure. Despite internal hostility, America's institutions have proven strong  — election workers, governors, judiciary, and Congress. I am relieved that Joe Biden is sworn in as President today and coming into the White House. I know that this feeling is shared by many people in Germany."

Nicola Sturgeon, Scotland’s first minister, pulled no punches, telling the Scottish Parliament Wednesday: "I'm sure many of us across the chamber and across Scotland will be very happy to say cheerio to Donald Trump today." Sturgeon also wished Biden and new Vice President Kamala Harris well.

Spanish Prime Minister Pedro Sánchez said at an event in Madrid on Wednesday: “Five years ago, we thought Trump was a bad joke, but five years later we realized he jeopardized nothing less than the world’s most powerful democracy.”

In his farewell video address Tuesday, Trump claimed: “We restored American strength at home and American leadership abroad. The world respects us again. Please don’t lose that respect.”

Not surprisingly, China and Iran also said they were hopeful for a better relationship with the Biden administration after Trump engaged in a trade war with China and withdrew the U.S. from the Iran nuclear deal negotiated during the Obama administration.

"In the past four years, the US administration has made fundamental mistakes in its strategic perception of China ... interfering in China's internal affairs, suppressing and smearing China, and causing serious damage to China-US relations," Hua Chunying, a Chinese foreign ministry spokeswoman, said at a news briefing Wednesday.

Hua said the Biden administration should “look at China rationally and objectively, meet China halfway and, in the spirit of mutual respect, equality and mutual benefit, push China-US relations back to the right track of healthy and stable development as soon as possible."

Iranian President Hassan Rouhani called on Biden to rejoin the nuclear pact and lift sanctions on his country. 

"If you fulfill all your obligations, we will fulfill all our obligations as well,” Rouhani said in a message directed to Biden during a cabinet meeting Wednesday. "If you do not do so, we will not bow down to you. If you do fulfill your obligations, we don't owe you anything.”

Many foreign leaders’ statements, however, were focused only on Biden and the future.

Canadian President Justin Trudeau tweeted: “Congratulations, @JoeBiden, on your inauguration as the 46th President of the United States. Our two countries have tackled some of history’s greatest challenges together - and I’m looking forward to continuing this partnership with you, @KamalaHarris, and your administration.”

British Prime Minister Boris Johnson released a statement saying he is looking forward to a close relationship with the Biden administration. 

"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," Johnson said.

French President Emmanuel Macron tweeted to Biden and Harris, “Best wishes on this most significant day for the American people!” and added, “We will be stronger to face the challenges of our time. Stronger to build our future. Stronger to protect our planet.”

Macron also welcomed the U.S. back into the Paris climate agreement, which is one of Biden’s top priorities as he takes office.

In Vatican City, Pope Francis said in a statement that he is praying Biden’s decisions “will be guided by a concern for building a society marked by authentic justice and freedom, together with unfailing respect for the rights and dignity of every person, especially the poor, the vulnerable and those who have no voice.” Biden is just the second Catholic to serve as U.S. president.

Israeli Prime Minister Benjamin Netanyahu congratulated Biden and Harris on what he called their “historic inauguration.” 

"President Biden, you and I have had a warm personal friendship going back many decades,” Netenyahu said in a video statement. “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.”