European Foreign Ministers today endorsed a “clear and strong response” to a chemical weapons attack that strongly points to the Syrian Government, but they urged the US to delay possible military action until UN inspectors report their findings.

US Secretary of State John Kerry, trying to make the Obama administration’s case for a strike, thanked the European Union for a “strong statement about the need for accountability.”

Kerry said he would share his counterparts’ concern with US officials. A senior State Department official who attended Kerry’s meeting with the ministers in Lithuania, said Kerry made clear that the US has not made any decision to wait.

The official spoke on condition of anonymity to disclose details about the private meeting.

Later, at a news conference in Paris with French Foreign Minister Laurent Fabius, Kerry said “this is not the time to be silent spectators to slaughter” and that “this is not the time to allow a dictator unfettered use of some of the heinous weapons on earth.”

Fabius said that “punishment is not at odds with a political solution. ... Bashar Assad will not participate in any negotiation as long as he sees himself as invincible.”

President Barack Obama has asked the US Congress to approve the use of force. A final vote in the US Senate is expected at the end of the coming week. A US House vote is likely in the week of September 16.

A statement read at the end of the Ministers’ meeting by the EU’s foreign policy chief, Catherine Ashton, said the August 21 attack was a “blatant violation of international law, a war crime and a crime against humanity.”

Information from a wide variety of sources confirmed the chemical attack, according to the statement, and “seems to indicate strong evidence that the Syrian regime is responsible” as it is the only party “that possesses chemical weapons agents and the means of their delivery in a sufficient quantity.”

The statement said a “clear and strong response is crucial to make clear that such crimes are unacceptable and that there can be no impunity.” But at the same time, the statement said the EU backs the need to address the crisis through the UN process.

The EU said it hoped a preliminary report of the investigation can be released as soon as possible and welcomed French President Francois Hollande’s statement yesterday to wait for this report before any further action is taken.