"We formally sent a letter to the United Nations, we asked them in that letter to send a delegation in order to investigate what happened in Khan Shaykhun," Assad said.
"Of course till this moment they haven't sent anyone, because the West and the United States blocked any delegation from coming, because if they come, they will find that all their narratives about what happened in Khan Shaykhun and then the attack on Sha'irat airport was a false flag, was a lie," he said.
Furthermore, Assad said that in the wake of the first attack in Aleppo carried out by terrorists against the army a few years ago, Damascus had asked the United Nations to send an investigation delegation "in order to prove what we said about the terrorists having used gas against our army."
"And later many incidents happened in that way, and they didn't send any delegation. It's the same now," Assad said.
Dmitry Egorchenkov, deputy head of the Institute for Strategic Studies and Prognosis at the People’s Friendship University of Russia, noted that the current situation proves that the West continues to apply double standards.
"Structures within the UN, first of all the Organization for the Prohibition of Chemical Weapons (OPCW), try to conduct some kind of a remote investigation.These organizations and structures have ignored other reports by Damascus about chemical weapons incidents in Syria. Our Western partners continue to follow the logic of double standards. Unfortunately, the UN is not independent and cannot have an impartial role in the investigation," Egorchenkov told Radio Sputnik.
According to the expert, the West is blocking the probe for a number of reasons.
"These organizations (the UN and the OPCW) are controlled by Western states. They are afraid of an impartial investigation because it may turn out that the incident was organized by West-backed forces. And if it turns out that the attack was fake this would mean it was part of an information war and this would be clear," Egorchenkov pointed out.
Meanwhile, earlier this week, the OPCW fact-checking mission investigating the alleged use of chemical weapons in Khan Sheikhun said it had found traces of sarin in the victims' bodies.
"The results of these analyses from four OPCW designated laboratories indicate exposure to Sarin or a Sarin like substance. While further details of the laboratory analyses will follow, the analytical results already obtained are incontrovertible," OPCW Director-General Ahmet Uzumcu said Wednesday.
The next day, the OPCW rejected the Russian and Iranian proposal to investigate the suspected chemical weapons incident in Syria’s Idlib.
According to ex-member of a UN commission on biological and chemical weapons Igor Nikulin, the OPCW probe cannot be considered objective in any way.
"Unfortunately, the hasty statements that they [OPCW officials] make without the commission's visit [to Idlib], without taking analyses on the ground, are of course alarming asthe footages we all saw don't necessarily mean that exactly sarin had been used, although it cannot be excluded. If the commission arrived at the site and took trial tests, then it would be logical. But they made a diagnosis from The Hague. It reminds of a diagnosis of a doctor who did not see his patient," he told Sputnik Radio.
Nikulin added that Damascus has been blamed for the alleged chemical attack that hadn't been properly investigated.
On April 4, a chemical weapons incident in Syria's Idlib Province claimed the lives of some 80 people and inflicted harm on an additional 200 civilians. The Syrian National Coalition of Revolutionary and Opposition Forces, as well as a number of Western states, accused the Syrian government troops of carrying out the attack, while Damascus refuted these allegations. The Syrian government has repeatedly said that the Syrian Army does not possess chemical weapons.
Russian President Vladimir Putin said on April 6 that groundless accusations related to the chemical weapons incident in Idlib Province were unacceptable before the investigation into the matter had been carried out.
However, the incident was used as pretext for the United States to conduct a missile strike against Ash Sha'irat Airbase on April 6. US President Donald Trump characterized the strike as a response to the alleged use of chemical weapons by Syrian government troops while Russian Foreign Minister Sergei Lavrov said it was a violation of international law. Iranian Supreme Leader Ayatollah Ali Khamenei described the US missile strike against the Syrian airfield as a strategic mistake.