"Any action of any type without the approval of Syrian government is an aggression against Syria," Ali Haidar, minister of national reconciliation affairs, told reporters in Damascus on Thursday. "There must be cooperation with Syria and coordination with Syria and there must be a Syrian approval of any action whether it is military or not."
Foreign countries could use the Islamic State threat simply as a pretext for attacking Syria, Haidar told reporters ahead of a meeting with new international peace mediator Staffan de Mistura.US President Barack Obama authorised late on Wednesday air strikes against Islamic State group targets inside Syria for the first time, pledging to destroy its fighters "wherever they exist". In an address to the nation, Obama also announced an expansion of strikes in Iraq, saying he would be dispatching nearly 500 more US troops to the country to assist its besieged security forces.
Obama called on Congress to authorise a programme to train and arm rebels in Syria who are fighting both the Islamic State group and Syrian President Bashar al-Assad. Syria's main Western-backed opposition group welcomed Obama's decision, but while repeating its demand that Assad must go.
"The Syrian Coalition ... stands ready and willing to partner with the international community not only to defeat ISIS [Islamic State] but also rid the Syrian people of the tyranny of the Assad regime," said Hadi al-Bahra, head of the coalition.
Russia said unilateral US strikes in Syria would be a crude violation of international law.
"The US president has directly announced the possibility of strikes by American armed forces against positions of the Islamic State in Syria without the consent of its legal government," said Alexander Lukashevich, a spokesman for the Russian foreign ministry. "In the absence of an appropriate decision of the UN Security Council, such a step would become an act of aggression, a crude violation of the norms of international law," he said.
Also on Thursday, the foreign ministers of Germany and Britain said they would not be taking part in air strikes in Syria against the armed group. British's Philip Hammond said the UK "supports entirely the US approach of developing an international coalition" against IS. But, asked by Reuters news agency about Obama's proposal for air strikes against IS in Syria, Hammond replied: "Let me be clear: Britain will not be taking part in any air strikes in Syria. We have already had that discussion in our parliament last year and we won't be revisiting that position."
He said the legal environment and "military permissiveness" in Syria and Iraq were very different.