Syrian President Bashar al-Assad has said that a suspected chemical attack on the rebel-held town of Khan Sheikhoun was "fabricated" as a pretext for the United States to strike his regime's forces, during an interview with AFP.

Assad went on to accuse the US of being "hand-in-glove with the terrorists" and said that his regime was unable to perpetrate such an attack because it had given up chemical weapons stockpiles years previously.

US President Donald Trump ordered a missile strike on a Syrian government airbase in response to the alleged chemical attack. The aftermath has seen tensions bubble between the US and Russia, whose troops are aiding Assad and were stationed at the airbase.

At a press conference in Moscow, US Secretary of State Rex Tillerson said that US was still confident in its assessment that the Assad regime had perpetrated the attack, adding that they believed the regime has used chemical weapons, including chlorine bombs, over 50 times.

A United Nations Security Council resolution condemning the use of chemical weapons in Syria was vetoed by Russia on Wednesday – the resolution, drafted by the US, UK and France, included a disputed paragraph that demanded investigators be given immediate access to the site.

After the vote, UK ambassador to the UN Matthew Rycroft said Russia had "abused its veto" to protect "a murderous, barbaric criminal", leading Russia's ambassador to launch an angry tirade against the UK envoy.

Both Trump and Tillerson have spoken of relations between the two superpowers being at a low point recently. During a press conference with Nato Secretary General Jens Stoltenberg, Trump said the US was "not getting along with Russia at all".