30 August 2013 Last updated at 09:25 GMT
Q&A: Threatened strike on Syria
Any Western action will likely have to wait until after UN inspectors have reported
A US-led military strike against Syria is looming in the aftermath of a suspected chemical weapons attack in Damascus, taking the crisis into a new phase. Here is a look at some of the issues surrounding the current tensions.
Why is military action being talked about now?
Many have posed the question of why the US and its allies are talking up the prospect of an intervention now when the conflict has already left around 100,000 dead, forced more than 1.7m Syrians to flee the country (with more internally displaced) and has increased tensions in neighbouring countries.
US President Barack Obama said last year that any use of chemical weapons by the Syrian regime of President Bashar al-Assad would be a "red line". After several alleged instances of chemical weapons use earlier this year, in June the US said its intelligence services had "high confidence" that they had indeed been used and that the US would as a result send unspecified military aid to the opposition.
However the events of 21 August, when a suspected chemical weapons attack left hundreds of people dead in the Ghouta area on the outskirts of Damascus, seem to have convinced Western powers that a stronger response was necessary. While reported death tolls vary, the Ghouta attacks stand as one of the deadliest incidents of the entire conflict, with horrific footage uploaded by activists showing scores of dead bodies, including many children.
US Secretary of State John Kerry said that "the indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders, by chemical weapons is a moral obscenity" and Western officials have said the killings cannot go unpunished.
Who would carry out a military strike?
The UK, France and the US were all quick to raise the prospect of military action - and have forces in place in the region that could be used in the event of a strike.
But UK Prime Minister David Cameron's plans to join US-led action were dashed after a vote in support of military intervention was rejected by Parliament on 29 August.
US Defence Secretary Chuck Hagel said the US would continue to seek out an "international coalition" for military action even if the UK is not involved.
French President Francois Hollande said France is still prepared to take action, even without British involvement.
In the region itself, Turkey has said it would be ready to take part in international action against Syria, even without UN approval.
What form would a Western military strike take?
The options for how it would be carried out range from limited "punitive strikes" to enforcing a no-fly zone over the country or trying to establish control over Syria's chemical weapons arsenal.
President Obama seemed to suggest that any strike would be limited in nature - as he put it to serve as a "shot across the bows" of the Syrian government rather than to try to tip the balance against it in the conflict.
What is the likely timeframe for any military action?
UN chemical weapons inspectors investigating the alleged attack in Ghouta are expected to leave Syria on 30 August and present their initial findings to the UN the following day.
A fresh push is then expected to be made at the UN Security Council for a resolution authorising action, even though this will almost certainly be blocked by Russia and China.
Although the White House has said it views the inspectors' mission as "redundant" because the US was already convinced Syria had used chemical weapons, it is thought Western powers will want to be seen as having exhausted all possible diplomatic avenues before taking action.
In addition, there has also been speculation that Western powers will not want to take action before or during a two-day G20 leaders' summit in Russia, scheduled to start on Thursday 5 September.
What have Syria and its allies said?
The Syrian government has strenuously denied that it has used chemical weapons. Syrian officials have suggested that the opposition were behind any such attacks and that they were encouraged in this by Western powers.
Syria's Deputy Foreign Minister Faisal Miqdad said on 27 August that Syria would "defend itself against any international attack" and warned it would trigger "chaos in the entire world".
Syria's key allies Russia and Iran have also been highly critical of any intervention. Russia has said there is no proof the Syrian government was behind the Ghouta attacks and has warned of "catastrophic consequences" of any intervention, calling it a "grave violation of international law". Although Russia is unlikely to be drawn into any direct confrontation, correspondents say it may increase weapons supplies to Damascus in retaliation.
Iranian Supreme Leader Ali Khamenei has said an intervention would be a "disaster". Other Iranian officials have in the past warned of consequences for the region and recently threatened Israel would be attacked in return. There has been speculation that Lebanese militant Shia movement Hezbollah, allied to Iran and which is fighting alongside government troops in Syria, might fire rockets against Israel in response to any Western strike.
