BERLIN (Reuters) - The European Union must become stronger in response to a weakening of democracy in the United States, Russia and Turkey,

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the leader of Germany’s centre-left Social Democrats said in remarks published on Saturday.

Martin Schulz, who is also a former president of the European Parliament, said that U.S. President Donald Trump, Russian President Vladimir Putin and Turkish President Tayyip Erdogan behaved like “autocratic rulers”.

“It is now important to rejuvenate Europe and make it stronger. Not only through words but also through concrete policies,” Schulz told the Passauer Neue Presse.

Chancellor Angela Merkel hosts leaders of the G20 leading economies at a summit in Hamburg on July 7-8, where Trump’s vow to renegotiate trade agreements and make them better for the United States is expected to be one of the most divisive topics on the agenda.

Opposition to Trump’s protectionist agenda is one area on which Schulz and Merkel agree. Schulz last month accused Trump of destroying Western values and undermining international cooperation.

“There are some in the G20 that behave like autocratic rulers: Turkish President Erdogan, Russian President Putin and also U.S. President Trump,” Schulz said.

Schulz’s SPD are 14 percentage points behind Merkel’s Christian Democrats (CDU) and their Bavaria-based Christian Social Union sister party three months before a national election on Sept. 24.

Trump wants Germany and other European allies to boost defence contributions to the NATO military alliance. He has criticized Germany’s large trade surplus with the United States.

Merkel said this week that open markets and free trade were a key focus of Germany’s G20 presidency.