"They fabricated the whole story in order to have a pretext" to attack the air base, Assad said in the interview, a video of which was released by his office.
The Syrian army on Thursday said the USA -led anti-terror coalition struck a chemical weapons depot controlled by the Islamic State (IS) group in eastern Syria, killing hundreds, including civilians.
"We again have a situation where the White House has issued an obviously false, misleading and amateurish intelligence report", he concluded, recalling the 2013 situation when the Obama administration claimed Assad had used chemical weapons against the rebels in Ghouta, near Damascus.
A man breathes through an oxygen mask as another one receives treatments, after what rescue workers described as a suspected gas attack in the town of Khan Sheikhoun in rebel-held Idlib, Syria April 4, 2017. However, the remaining two facilities were in territory controlled by the rebels, he said, and it remains unclear what happened to the chemicals stored there.
Tests have confirmed sarin gas was used in Khan Sheikhoun, Syria.
"Our firepower, our ability to attack the terrorists hasn't been affected by this strike", he said.
The toxic gas attack on April 4, which killed scores of children, prompted the United States to launch missile strikes on a Syrian air base and widened a rift between the United States and Russian Federation, a close Syrian ally. "These have tested positive for the nerve agent Sarin, or a Sarin-like substance", the delegation said during a special session at the Organisation for the Prohibition of Chemical Weapons in The Hague.
Russian Federation has called for a thorough investigation by the Organisation for the Prohibition of Chemical Weapons (OPCW) of the allegations of chemical weapons use in Khan Sheikhun.
The Syrian army meanwhile issued a statement saying that the US -led coalition attacked a position of the Islamic State group in the eastern province of Deir el-Zour, killing hundreds of fighters and civilians, many of them from poisonous gas.
Matthew Rycroft told the Security Council: "The United Kingdom therefore shares the USA assessment that it is highly likely that the regime was responsible for a sarin attack on Khan Sheikhoun on 4 April". The American leader also announced a missile strike targeting an air base believed to be the source of the chemical weapons used in the attack.
American officials reportedly see the hospital bombing as an attempt to cover up the use of chemical weapons.
Its findings, expected in three to four weeks, will be passed to a joint United Nations-OPCW chemical weapons investigation.
Investigators have concluded that sarin, chlorine and sulfur mustard gas have been used in Syria's civil war.