ROME—President Joe Biden and European leaders said they shared grave concern about Iran’s escalating efforts to enrich uranium and called on the country’s new president to change course.

French President Emmanuel Macron, British Prime Minister Boris Johnson and German Chancellor Angela Merkel joined Mr. Biden at a summit of the Group of 20 major economies in Rome to discuss Iran’s nuclear efforts.

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ROME—President Joe Biden and European leaders said they shared grave concern about Iran’s escalating efforts to enrich uranium and called on the country’s new president to change course.

French President Emmanuel Macron, British Prime Minister Boris Johnson and German Chancellor Angela Merkel joined Mr. Biden at a summit of the Group of 20 major economies in Rome to discuss Iran’s nuclear efforts.

In a joint statement, the leaders said they shared the goal that Iran should not develop or acquire a nuclear weapon. They said that since nuclear negotiations with Tehran have stalled, the country’s new hard-line government has accelerated nuclear activities that have no civilian purpose, saying that future advances would jeopardize any return to the 2015 nuclear accord with major international powers.

“We are convinced that it is possible to quickly reach and implement an understanding on return to full compliance and to ensure for the long term that Iran’s nuclear program is exclusively for peaceful purposes,” they said. “We call upon President (Ebrahim) Raisi to seize this opportunity and return to a good faith effort to conclude our negotiations as a matter of urgency,” the statement said.

Mr. Biden is seeking to revive the nuclear deal, called the Joint Comprehensive Plan of Action, which strictly but temporarily constrained Iran’s nuclear activities in return for lifting economic sanctions. Since former President Donald Trump withdrew the U.S. from the deal in 2018, Iran has breached most of the limits.

Ahead of the meeting, reporters asked Mr. Biden when he would like to see the negotiations with Iran resume. “They’re scheduled to resume,” he answered.

For President Biden, the summit follows a period of diplomatic tensions on the world stage.

Photo: POOL/REUTERS

Iran’s chief negotiator recently said the country would return to the talks after a five-month hiatus. U.S. and European officials have been cautious about the prospects of reaching an agreement with President Raisi’s government.

White House national security adviser Jake Sullivan told reporters Thursday that it was “not entirely clear to me yet” if Iran’s government was ready to return to talks, saying “I think we’ll have to wait and see when and whether they actually show up at the negotiating table.” He said the U.S. is prepared to negotiate in “good faith” and “we hope they are as well.

Earlier, G-20 leaders gave their blessing to an agreement among nearly 140 countries to overhaul global tax rules, with Mr. Biden stressing that it was a historic deal during the opening session, according to the White House. The reform sets out a global minimum corporate tax rate of 15% for large international businesses, aimed at preventing companies from exploiting low-tax jurisdictions. It now must be implemented by signatory nations, including the U.S., which could prove challenging in the divided Congress.

Climate change is another focus of the Rome summit, which will set the tone for two weeks of global talks on climate change in Glasgow, Scotland that immediately follows the Rome meeting. The G-20 leaders are attempting to find a common position on how to best adhere to the 2015 Paris climate agreement, which calls on countries to start reducing their greenhouse-gas emissions as soon as possible and achieve a climate-neutral world by midcentury.

But leaders are split over phasing out coal and measures aimed at limiting global warming to 1.5 degrees Celsius. Finding agreement on concrete policies could prove challenging. Key topics of discussion will include the use of coal, as well as whether to end subsidies for fossil fuels more broadly.

Mr. Johnson spoke Friday to Chinese President Xi Jinping, who isn’t attending in person, and pressed him to make China’s climate targets more ambitious.

China has said it aims for carbon emissions to peak before 2030. “I pushed a bit on that,” said Mr. Johnson, who suggested they aim for 2025 instead. “I wouldn’t say he committed to that,” said the British leader. “He said, ‘Look China depends on coal,’” said Mr. Johnson of Mr. Xi’s response. Mr. Johnson pointed out that the U.K. used to be reliant on coal and now needs it for only around 1% of electricity generation. “It shows you just how fast you can make the transition,” he said.

President Biden with British Prime Minister Boris Johnson, French President Emmanuel Macron and German Chancellor Angela Merkel on the sidelines of the summit.

Photo: brendan smialowski/Agence France-Presse/Getty Images

Mr. Johnson, who will host the climate talks in Glasgow, known as COP26, played down what could be achieved there and at this weekend’s Rome G-20 summit.

“There is no chance of us getting an agreement next week to limit climate change to 1.5 degrees,” he said Saturday. “What we could conceivably do if everybody gets their act together... is get an agreement that means that COP26 in Glasgow is a way station that allows us to end climate change and allows us to keep alive that dream of restricting the growth to 1.5 degrees.”

In a veiled criticism of developed countries that haven’t fulfilled their previous climate pledges, Mr. Xi said during the phone call with Mr. Johnson that countries should transform their high ambitions into concrete actions, according to Chinese state news agency Xinhua.

Mr. Xi told the G-20 summit in a speech delivered by video on Saturday that developed countries should set an example on emissions reduction, take the challenges of developing countries into account and provide financial and technical support to them, Xinhua said.

Money is a sticking point in climate-change negotiations around the world. As economists warn that limiting global warming to 1.5 degrees Celsius will cost many more trillions than anticipated, WSJ looks at how the funds could be spent, and who would pay. Illustration: Preston Jessee/WSJ The Wall Street Journal Interactive Edition

On Sunday, Mr. Biden will host a meeting on the supply-chain issues that have been disrupting much of the world’s economic rebound from the Covid-19 pandemic, leading to bottlenecks, production shortages and rising consumer costs in the U.S. and elsewhere.

Mr. Biden will have a bilateral meeting Sunday with Turkish President Recep Tayyip Erdoğan, said a senior administration official. The meeting comes at a tense moment between the countries, as relations have soured over clashing interests in the war in Syria, human rights issues within Turkey, and Ankara’s purchases of Russian arms systems.

The U.S. leader will attend the Glasgow climate summit Monday and Tuesday. He has been seeking domestic agreement on legislation covering climate change and social spending, and tried to wrangle a deal in Congress before leaving Washington on Thursday. But the $1.85 trillion framework he outlined before flying to Rome didn’t immediately persuade progressives to approve a parallel infrastructure bill worth roughly $1 trillion.

For the G-20 summit, Italian authorities have implemented stringent security measures across the city of Rome, particularly in the district called EUR where the leaders are gathering. Italy’s government has deployed around 10,000 members of police and military forces to ensure security. Two demonstrations by around 5,000 environmentalists, labor unions and antigovernment protesters began in central Rome Saturday early afternoon, far from the summit venue in the city’s south. A small group of environmentalists this morning blocked a road close to the venue of the summit, disrupting traffic. Police removed them quickly.

Italian authorities will watch the different demonstrations closely as some protests against Italy’s strict Covid-19 vaccination rules recently have been infiltrated by violent protesters

President Biden, the second Catholic president in U.S. history, greeted Pope Francis at the Vatican. The meeting agenda includes issues such as climate change, ahead of the U.N.’s COP26 summit in Glasgow. Photo: VaticanMedia/Picciarella/Zuma Press The Wall Street Journal Interactive Edition

—Max Colchester and Sha Hua contributed to this article.

Write to Catherine Lucey at catherine.lucey@wsj.com and Giovanni Legorano at giovanni.legorano@wsj.com