Syria’s President Bashar-al Assad says reports of a chemical attack by his forces were “one hundred percent fabrication”.
In an exclusive video interview with Agence France-Presse, Assad insisted that “there was no order to make any attack.”
More than 80 people were killed in the rebel-held town of Khan Sheikhoun on 4 April, and hundreds suffered symptoms consistent with a nerve agent.
Witnesses said they saw warplanes attack the town but Russia says a rebel depot of chemical munitions was hit.
Shocking footage showed victims – many of them children – convulsing and foaming at the mouth.
Sufferers were taken to hospitals across the border in Turkey, which opposes President Assad.
Turkey has since said it has “concrete evidence” that the nerve agent Sarin was used.
Assad told the AFP news agency that the Syrian government gave up its arsenal of chemical weapons in 2013, adding “even if we have them, we wouldn’t use them”.
However, since 2013, there have been continued allegations that chemicals such as chlorine and ammonia have been used against civilians in the ongoing civil war.
The Syrian government has repeatedly denied using them, blaming rebel groups in some instances.
Assad accused the West of making up events in Khan Sheikhoun so it had an excuse to carry out missile strikes on the government’s Shayrat airbase, which took place a few days after the alleged attack.
“It’s stage one, the play [they staged] that we saw on social network and TVs, then propaganda and then stage two, the military attack,” he said, questioning the authenticity of the video footage.
He also said Khan Sheikhoun, in Syria’s north-western Idlib province, had no strategic value and was not currently a battle front.
Western allies say there is compelling evidence that the Syrian government was behind what happened in Khan Sheikhoun.
They reacted angrily on Wednesday after Russia, Syria’s key ally, vetoed a draft resolution at the UN Security Council – the eighth time it has done so over the Syrian conflict.
President Assad told the AFP that he would only allow what he called an “impartial” investigation to ensure it would not be used for “politicised purposes”. But he did not give further details.
The BBC’s Sebastian Usher notes the Syrian leader looks greyer and more drawn than in recent interviews.
The US strikes on Shayrat airbase and a reversal of what had been a growing diplomatic acceptance that Mr Assad’s removal was no longer a priority may have taken its toll, our correspondent adds.
More than 300,000 people have lost their lives and millions of people have been displaced since a peaceful uprising against Mr Assad six years ago turned into a full-scale civil war.