The European Union on Saturday urged a “clear and strong” response to the alleged chemical-weapons attack in Syria last month that left almost 1,500 people dead, including hundreds of children.

Speaking at a meeting of EU foreign ministers in Vilnius, Lithuania, Catherine Ashton, the EU’s senior foreign-policy official, said “strong evidence” indicates that the government of Syrian President Bashar Assad carried out a chemical-weapons attack on Aug. 21, which she called “a blatant violation of international law, a war crime and a crime against humanity.”

But Ashton stopped short of calling for a military strike, and instead echoed the opinion of French President Francois Hollande, who on Friday said his government would wait for United Nations inspectors to finish their investigation.

U.S. President Barack Obama, initially suggesting immediate action was necessary, has since sought congressional approval for a strike. Members of both houses of Congress are expected to debate the issue on Monday when they return from their recess. Meanwhile, a U.N. report could be submitted as soon as Sept. 15, according to a diplomat cited by the New York Times.

Ashton, who was joined at the meeting by U.S. Secretary of State John Kerry, said the international community “cannot remain idle” in the face of blatant human-rights abuses.

“The EU urges the U.N. Security Council to unite in its efforts to prevent any further chemical attack,” Ashton said in follow-up remarks. “To that effect, it encourages the UNSC to fulfill its responsibilities and take all initiatives to achieve this goal. The EU and its member states intend to play a full and active part in that context.”

Read Ashton’s full remarks here or watch video of them below.