Germany not keen to join France and UK on Syria strike

He added that a Western strike could create a "spiral of escalating violence" by drawing Iran and the Lebanese militant group, Hezbollah, deeper into the conflict.

He also said military action without a UN mandate is "hard to imagine."

Despite Missfelder's statement, Merkel in recent days joined British and French leaders in giving credence to reports the Syrian regime has used chemical weapons to kill hundreds of people on the outskirts of Damascus.

A statement by British Prime Minister David Cameron's office noted that Cameron and Merkel spoke by phone on Sunday.

"They agreed that this was a very grave incident and that there was little doubt that it had been carried out by the regime," it said.

"They agreed that such an attack demanded a firm response from the international community," it added.

France on Monday also used strong words.

"The only option that I am ruling out is to do nothing," French foreign minister Laurent Fabius said on Europe 1 radio.

The toughest language came from Washington on Monday evening, however.

US secretary of state John Kerry told media in the US capital: "The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders, by chemical weapons is a moral obscenity."

He added: "There must be accountability for those who would use the world's most heinous weapons against the world's most vulnerable people."

The US also cancelled a meeting with Russia, due in The Hague on Wednesday, designed to re-launch peace talks between Syrian rebels and Syrian authorities.

If the US and some EU countries do strike Syria's chemical weapons depots, elite brigades or air force, the move risks further alienating Moscow.

Cameron's office said he also spoke with Russian President Vladimir Putin on Monday, but "the Russian President said Moscow had no evidence as to whether such an attack had taken place or who was responsible."

Russian foreign minister Sergei Lavrov on Monday spelled out his country's point of view.

“We are especially concerned to hear talk coming from London and Paris suggesting that Nato could take the lead in bombing in Syria without Security Council approval. This is a very slippery slope," he told Russian press.

"Any military action without [UN] Security Council approval would be a crude violation of international law," he noted.

Asked what Russia would do if a Nato-linked coalition does strike its Middle East ally, Lavrov added that Moscow is "not planning to go to war with anyone," however.

A UN chemical weapons inspection team arrived on the site of the alleged attack on Monday, with any Western action unlikely to come before it files its report.

A former French airforce chief, Jean Rannou, told EUobserver in a previous interview a military strike would most likely be launched from the UK's military base in Cyprus.

He noted there is a risk that Syria's Russian-made SA-17 missiles could shoot down a handful of Nato planes.

But he added: "I don't see any purely military problems. Syria has no defence against Western systems."

Some defence analysts have also voiced concerns about asymmetric threats.

EU countries have troops in UN peacekeeping missions in Lebanon and Syria, which could become targets.

Rainer Wendt, the head of Germany's police trade union, also told press on Monday that Syria could react with terrorist attacks in EU countries, including Germany, whether or not it takes part in an assault.