Trump: Syria is now 'my responsibility' following chemical weapons attack

US President Donald Trump has said that the Syrian conflict has now become his responsibility after the use of chemical weapons during an attack against civilians on Wednesday.

Trump referred to the attack as "heinous" and an "affront to humanity", with local activists reporting that Syrian president Bashar al-Assad's regime was responsible for the attack.

The civil war in Syria began in 2011 and has since seen hundreds of thousands of people killed in a bloody conflict, many of those children, with the UN having said Assad has previously used chemical weapons.

"I now have responsibility, and I will have that responsibility and carry it very proudly," Trump said following a White House statement on the attack northern Syria.

"Yesterday's chemical attack, a chemical attack that was so horrific in Syria against innocent people, including women, small children and even beautiful little babies, their deaths were an affront to humanity."

The president argued that the Obama administration was partly to blame for allowing the conflict to continue, saying his predecessor's failure to respond "was a blank threat that set us back a long ways, not only in Syria but in many other parts of the world".

Assad’s government and Russia, which backs Assad's regime, have sought to shift the responsibility for the attack towards rebel groups. Russia has threatened to veto any UN resolution that punishes Syria.

The United Nations held an emergency security meeting on Wednesday in order to discuss the issue, where US ambassador Nikki Haley hinted that if the UN Security Council failed to act, the US might do so.

Holding aloft gruesome photographs of child victims from the gas attack, she said: "We cannot close our eyes to those pictures. We cannot close our minds."

When US Defense Secretary James Mattis was asked by reporters at the Pentagon about a possible US response, he said "it was a heinous act and will be treated as such".