Mr Hague hinted the government was ready to launch an armed response to the Syrian civil war after around 300 people were reportedly killed in a chemical attack.
He said the UN security council had not "shouldered its responsibilities" on Syria because Russia and China have resisted military intervention.
But the Tory minister argued it was possible to respond to the use of chemical weapons "without complete unity" on the council.
Defending the prospect of a unilateral attack with the US, he said: "Otherwise it might be impossible to respond to such outrages, to such crimes."
Mr Hague's comments come before a meeting of Britain's National Security Council on Wednesday which PM David Cameron has returned from holiday to chair.
MPs from all parties immediately called for an emergency session of Parliament to debate whether Britain should wade into the war.
Labour shadow foreign secretary Douglas Alexander said: "If, in reality, the Prime Minister is now considering military options involving UK personnel then of course I would expect him to seek a recall of Parliament."
He insisted Mr Cameron should "come to the House of Commons and make his case in advance of a decision being made."
Opposition forces accused government troops of being behind last week's reported gas attack but President Bashar al-Assad dismissed the claim as "politically motivated."
Distressing but unverified footage of dead bodies and hospitalised children emerged after the reported incident.
Veteran Labour MP Paul Flynn urged leaders today to make a "rational response" to the "terrible pictures of the atrocity in Syria."
He said: "Instinctively we all want to punish the perpetrators and ensure there will be no repeat of this mass slaughter. That's the emotional reaction.
"The rational one is to measure the consequences of our using force in the Syrian civil war."
Mr Flynn added that both sides in the conflict have complex interests and said the consequences of intervention were completely unpredictable.
And he warned: "A civil war with evil fanatics on both sides could quickly escalate into a regional war and a world war."
Meanwhile UN experts sent to investigate the reported gas attack were prevented from reaching the area today by unidentified snipers.
Mr Hague speculated that there was "no other plausible explanation" than that the Syrian army are delaying inspectors to try and cover up its alleged attack.
A message posted on Twitter by the UN said: "Team replacing vehicle and then returning to area."