A US missile strike on an airbase in central Syria early on Friday was "foolish and irresponsible," President Bashar al-Assad's office said.
"What America did is nothing but foolish and irresponsible behaviour, which only reveals its short-sightedness and political and military blindness to reality," a statement said.
The US fired a barrage of 59 cruise missiles at the Shayrat base in response to a suspected chemical attack on a rebel-held town on Tuesday widely blamed on the Damascus regime.
The Syrian government has categorically denied the accusation, saying it had struck an arms depot belonging to a jihadist group.
Assad's office said the government would redouble its efforts against rebel groups after the US strike -- the first direct military action by Washington against the Damascus regime.
"This aggression has increased Syria's determination to strike these terrorist agents, to continue crushing them and to speed up the pace of work on this, wherever they are on Syrian territory," it said.
"The disgraceful act of targeting a sovereign state's airport demonstrates once again that different administrations do not change deeper policies."
The massive strike -- US President Donald Trump's biggest military decision since taking office -- marked a dramatic escalation in American involvement in Syria's six-year civil war.
It followed days of outrage at images of dead children and victims suffering convulsions from the suspected sarin gas attack on the rebel-held town of Khan Sheikhun.
An unnamed foreign ministry official quoted by Syrian state news agency hinted the footage was fabricated to preempt the strike.
"What happened in Khan Sheikhun was a premeditated act aimed at justifying the US strike on the Syrian army, which has confronted and continues to confront terrorism," the official said.
On Thursday, Syrian Foreign Minister Walid Muallem repeated the government's denial that it used chemical weapons on Khan Sheikhun at dawn, saying warplanes had instead targeted a jihadist warehouse.
"The first air raid conducted by the Syrian army was at 11:30 am (0830 GMT) on that day (Tuesday) and it attacked an arms depot belonging to Al-Nusra Front that contained chemical weapons," Muallem said.
An image grab taken from the state-run Syrian news channel reportedly shows a view of the Shayrat (,ash-Shairat,) airfield at the Syrian government forces military base, southeast of the central and third largest Syrian city of Homs.
