BIARRITZ, France — European Council President Donald Tusk on Saturday said escalating trade tensions between President Trump and other world leaders risk throwing the world into recession, bemoaning “senseless disputes” that had ripped countries apart.

“This may be the last moment to restore our political community,” he told reporters at the beginning of the Group of Seven summit here.

Tusk’s comments came one day after Trump and Chinese President Xi Jinping dramatically escalated a fierce trade war between the two countries. Tusk is attending the G-7 summit with Trump and leaders from France, Germany, the United Kingdom, Italy, Canada and Japan, and he said the summit comes at a perilous time.

“Trade wars will lead to recession while trade deals will boost the economy,” he said.

In response to a question, Tusk questioned Trump’s motivation in trade wars launched by the United States.

“For me it’s absolutely clear that if someone, for example . . . the United States and President Trump, uses tariffs and taxation as a political instrument, tool for some different political reasons, it means that this confrontation can be really risky for the whole world, including the E.U.,” Tusk said. “This is why we need the G-7.”

But in a sign that leaders are bracing for things to only get worse, Tusk said the E.U. was ready to retaliate against Trump if the U.S. leader followed through on some of his trade-related threats directed at France. Trump has said he will impose tariffs on French wine because France recently imposed taxes that impact U.S. technology companies.

“If the U.S. imposes tariffs on France, the E.U. will [respond] in kind,” he said.

Tusk also blasted Trump’s request to have Russia rejoin the G-7. Russian President Vladimir Putin has been excluded since 2014 after he invaded Ukraine and annexed Crimea. Europeans feel that welcoming him back would send a signal that they are ready to move on from the conflict. Tusk criticized Trump’s comments last year that Russia’s annexation of Crimea was somehow justified.

“Under no condition can we agree with this logic,” Tusk said.

Tusk and Trump have clashed in the past. Last year, Tusk vented that “with friends like that, who needs enemies,” after Trump pulled out of the Iran nuclear deal and threatened U.S. tariffs on E.U. steel and aluminum exports.

Advisers to some of the other leaders at the summit said that they were resigned to having a meeting in which relatively little is agreed upon, and a best-case scenario in which they escape without having been bloodied by Trump’s angry tweets. One official said that Trump’s combative history at the summits was reducing the utility of the gathering, thus reducing U.S. power as well.

But the Europeans enter the summit divided. A day before the meeting was scheduled to start, French President Emmanuel Macron announced his opposition to a trade deal between the European Union and South America’s Mercosur nations because of the fires and deforestation in the Amazon. A spokesman for German Chancellor Angela Merkel quickly said she didn’t think that was the right approach.

Germany, Italy and France are also arrayed against Britain in increasingly contentious Brexit negotiations. Leaders are growing resigned to the possibility Britain may crash out of the European Union on Oct. 31 without a transition deal in place to ease the economic shock for both sides.

Tusk said there were a range of issues he hoped would be addressed.

“I hope that we will be wiser after our meeting here,” he said.

The center of Biarritz, a 19th-century French resort town, was silent Saturday after being largely shut down by security. The Grande Plage — the long, sandy beach that fronts the palace-turned-hotel where leaders were gathering — would normally be packed with vacation-goers on a sunny August weekend. But on Saturday the seagulls had only the crashing waves for company as the fierce tide rolled onto the sand.