April 26, 2017 1154 GMT
The White House said on Tuesday that that US intelligence had confirmed that the government of President Bashar al-Assad used sarin gas on its own people and Moscow was engaged in a cover-up of Damascus’s role in the attack.
The allegations were made in a four-page report prepared by the White House National Security Council which contains declassified US intelligence on the attack and an answer to Syrian and Russian statements that foreign-sponsored militants carried out the gas attack to frame the Syrian government.
The report went on to claim that Damascus and Moscow had issued “false narratives” to mislead the world.
The document came as Tillerson arrived in Moscow on Tuesday to hold talks with Russian officials regarding the Syrian crisis. According to reports, Tillerson is to urge the Russian leadership to withdraw support from Assad.
On Monday, a US official, speaking condition of anonymity, told the Associated Press that the US has concluded that Russians knew ahead of time that chemical weapons would be used in the attack that left more than 80 people dead and dozens others injured in the town of Khan Shaykhun in Idlib province.
The United States, however, has no proof of Russian involvement in the actual chemical attack, the official acknowledged.
Two US Navy destroyers fired 59 Tomahawk cruise missiles from the Mediterranean Sea at al-Shayrat airbase in Homs province in western Syria on April 7.
US President Donald Trump said he had ordered the strike in response to the April 4 chemical attack in the Arab country that he blamed on the Syrian government.
The Syrian government has strongly denied responsibility for the gas attack, and there is no evidence that it was behind the assault.
The US along with the UK and France has also prepared a draft resolution to oblige the Syrian government to cooperate with an international probe into the attack. The draft resolution will be put to the vote at the UN Security Council on Wednesday.