Diplomatic pressure on Syria has failed and the UK is considering its response to a suspected chemical attack, Foreign Secretary William Hague says.
He told the BBC it would be possible for the UK and its allies to respond to the incident without the unanimous backing of the United Nations.
He said the UN Security Council, which is split over Syria, had not “shouldered its responsibilities”.
Any response would be “in accordance with international law”, he added.
The suspected chemical attack took place on Wednesday near the Syrian capital Damascus, and reportedly killed more than 300 people.
Mr Hague told BBC Radio 4’s Today programme that while he could not go into options or the timetable for action, he was not “going to rule anything in or out”.
“We, the United States, many other countries including France, are clear that we can’t allow the idea in the 21st century that chemical weapons can be used with impunity,” he said.
When asked about requests for the recall of Parliament, he said the UK had a “good record” of consulting MPs if the decision was to take military action.
David Cameron is under increasing pressure to recall Parliament to debate the Syrian crisis before Britain launches any missile strikes.
Labour has led the calls but it’s a view shared by many Conservative backbenchers.
Sarah Wollaston has indicated she would oppose any military intervention in Syria that didn’t have the full backing of the UN.
Given that, the comments by the Foreign Secretary William Hague – that it would be possible to respond to the chemical weapons attack in Syria without the unanimous backing of the UN – are likely to concern those MPs opposed to intervention.
Mr Cameron will be aware of the risks of recalling Parliament and allowing MPs to vote as he knows that a considerable number of them don’t back military intervention.
But, if he doesn’t, he’ll be accused of ignoring the will of his backbenchers.
Mr Hague said diplomatic methods to resolve the civil war in Syria had “failed so far”.
“We’ve discussed over the last year the small-scale chemical attacks that the regime has carried out over the last year.
“On every occasion we have given direct messages, sometimes passed to the United Nations, to the Syrians not to do that.
“We’ve discussed it with the Russians and indeed sometimes the Syrians have heard from the Russians and the Iranians that they should not conduct chemical attacks.”
Russia has continued to support the Syrian regime and Mr Hague said there would have been a “better chance of bringing this conflict to an end a long time ago” if the security council had been united.
But any action could be taken “without complete unity on the UN Security Council” or else it would be impossible to respond to “such outrages” , he added.
He suggested a response could be “based on great humanitarian need and distress”.
The foreign secretary repeated his assertion that last week’s suspected chemical attack was carried out by the regime of Syrian President Bashar al-Assad and that there was “no other plausible explanation”.
President Assad says the claims are “politically motivated” and defy logic as the regime has forces near the area.
UN inspectors are heading to the site of the suspected attack but Western governments have criticised Syria for taking too long to give the team access.
Prime Minister David Cameron was involved in a round of phone calls with fellow leaders, including US President Barack Obama, over the weekend, who agreed on the need to take “strong action”.
There has been some speculation about an imminent military strike against Syria but the BBC’s Middle East editor Jeremy Bowen said it was “a little premature”.
In addition to waiting for the UN inspectors to finish their work and talking to the UN Security Council, there would still be concern about military action.
“The worry about the uncertain, unknown, difficult and dangerous consequences is still there,” he said.
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