The ministry said in a statement on Saturday that the United States remarks about the use of chemical weapons in the Eastern Ghouta region of the east of the capital Damascus are "false claims", Xinhua news agency reported.
He said he was not rebutting the reports. "Clearly we are dealing with the Assad regime that has used denial and deceit to hide their outlaw actions", he remarked.
Unconfirmed intel has recently reported to the Pentagon that Syrian forces have weaponized chlorine and sarin gas.
The Trump administration on Thursday accused Syrian President Bashar Assad's government of producing and using "new kinds of weapons" to deliver deadly chemical poisons. The colorless toxin can cause respiratory failure, leading to death.
He said that non-governmental organizations and fighters on the ground in Syria had reported sarin use, and that the US was looking into the matter.
China opposes new USA nuclear strategy
Iran's nuclear deal, reached with six world powers, lifted some global sanctions in exchange for curbs to its nuclear programme. China has also long maintained it will never allow first use of its atomic weapons.
The Syrian government denied the accusations, saying it's rebels who mounted the attack to frame the government and draw in a military action from the US.
"We are on the record and you all have seen how we reacted to that, so they would be ill-advised to go back to violating the chemical (weapons) convention", Mattis added.
France said on Friday it was "deeply concerned" that Syria's government was flouting its pledges to stop using chemical weapons and Paris was working with its partners to shed light on recent suspected toxic gas attacks.
"The Foreign Ministry decisively condemns U.S. groundless allegations against the Syrian leadership of chemical weapons use in Eastern Ghouta [in eastern suburbs of Damascus]", the statement read, as quoted by the Syrian state-run SANA news agency. France says affiliated companies based in multiple countries have been furnishing materials for the manufacture of chemical weapons, including sarin gas.