"Those who believe that additional sanctions against Russia can help solve the crisis in Syria are extremely naive," Juncker said in an interview to the German ZDF broadcaster.
The European Commission president also spoke out against sending EU troops to Syria.
"I do not think that many Europeans want to die in Syria," Juncker said.
The European Union and its allies introduced several rounds of anti-Russia sanctions over Crimea rejoining Russia in 2014 and over Moscow's alleged involvement in the conflict between the eastern Ukrainian militia and Kiev. Russia has repeatedly refuted the allegations, warning that the Western sanctions are counterproductive and undermine global stability.
The situation in Syria will be discussed at the EU summit on Thursday.
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