Syrian President Bashar al-Assad dismissed reports last week's chemical weapons attack - widely blamed on his regime - as "100%" fabrication.
He claimed the USA and the West were "hand-in-glove with the terrorists".
Russia's foreign minister says Moscow expects the United Nations' chemical weapons watchdog to conduct an extensive probe into last week's chemical attack in Syria.
The deadly toxic gas attack has been widely blamed on Syria's President Assad and prompted the USA to retaliate with a cruise missile strike on one of the country's airbases.
"It's certainly possible. I think it's probably unlikely, and I know they are doing investigations into that right now", President Trump said during a news conference Wednesday. It was not allowed to film the interview itself; instead, the encounter was filmed by the Syrian presidency.
"They said there was no consensus on whether the Russians were involved in the attack or had foreknowledge of it", he adds.
But Assad, who appeared relaxed, said it was "not clear whether it happened or not, because how can you verify a video? You have a lot of fake videos now".
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The incident injured five children; two of the children were seriously injured after they fell from the house to the ground. A witness said the bouncy house was anchored down with stakes and straps.
The attack on the town of Khan Shaykhun killed scores of people, including numerous children. "Were they dead at all".
Using the incident as a pretext, United States warships in the Mediterranean launched a barrage of 59 Tomahawk missiles against Shayrat Airfield in Syria's Homs Province on April 7.
The Organisation for the Prohibition of Chemical Weapons said experts had analysed available information "and their preliminary assessment was that this was a credible allegation".
World leaders had called for an worldwide probe into the attack in Khan Sheikhoun last week, which prompted a retaliatory U.S. missile strike on a Syrian airbase.
He said his forces had not been diminished by the United States strike.
He said that India believed that it was important to defeat terrorism "which in that particular theatre is represented, among others by the IS (Islamic State) and cooperation of all countries is vital to achieving this objective". "They want to use it as an umbrella for the terrorists", said the Syrian president.
According to Syrian state news agency SANA, the US air strike has killed nine civilians, including four children.
On Wednesday, UN Security Council is due to hear a briefing of the UN Envoy for Syria Staffan de Mistura on the recent political developments in the country.