One of his deputies went further, telling Russia's state-owned news agency: "In general, primitiveness and loutishness are very characteristic of the current rhetoric coming out of Washington". It was Assad's first since the alleged April 4 chemical weapons attack prompted a United States cruise missile strike on a Syrian air base.
Lavrov insisted that facts had yet to be determined and Putin accused the Trump administration of fabricating the evidence to create a fake confrontation.
"Definitely, 100 percent for us, it's fabrication", Assad said in the video released by his office.
"There were no signs that would support the statement, the allegation that chemical agents were used there at all", Lavrov said.
Mr Trump, who strongly criticised the transatlantic alliance - which was formed in 1949 to counter the threat of the Soviet Union - during his election campaign, underlined the importance of the organisation during a press conference with Mr Stoltenberg.
But the final draft includes a paragraph that the Russians objected to last week stressing Syria's requirement to provide investigators with flight plans and information about air operations on April 4 when Khan Sheikhoun was attacked, names of helicopter squadron commanders, and immediate access to air bases where they believe an attack may have been launched.
He had said it was "obsolete because it was designed many, many years ago".
Iranian President Rouhani registers to run in May for a second term
During the previous presidential election in June 2013, Rouhani garnered 50.7 percent of a total of over 36 million votes. Ahmadinejad previously served two four-year terms from 2005 to 2013.
Russian Federation has criticized previous investigations carried out by the OPCW and the United Nations which blamed the Syrian government for at least three chemical weapons attacks without visiting the sites.
Lavrov said he emphasized the need for a wide-ranging OPCW probe during Wednesday's talks in Moscow with U.S. Secretary of State Rex Tillerson, suggesting that Western nations, Russian Federation and some regional powers could dispatch additional experts to join the investigation.
The strong comments by Kenneth D. Ward, the American ambassador to the Organization for the Prohibition of Chemical Weapons, came amid ongoing diplomatic skirmishes over last week's deadly attack in Syria.
Following talks that also involved Vladimir Putin, Tillerson announced that "There is a low level of trust between our two countries", and things only got more tense from there. "The world's two foremost nuclear powers can not have this kind of relationship".
The high-level talks in Moscow clearly failed to bridge the widening gap between the USA and Russian Federation on Syria.
But he said Moscow and Washington had agreed to continue co-operating to try to find a political solution for Syria.