Syria crisis: As US prepares to reveal intelligence on suspected Damascus chemical weapons attack, what do we know already?

Questions still remain over the much cited but yet to be revealed evidence

Parents grieve over the body of their child killed in a suspected chemical attack in Damascus (Rex)

With preparations for a Western attack on Syria seemingly well underway, many questions still remain over the much cited but yet to be revealed intelligence that is said to implicate the government of Bashar al-Assad in a chemical weapons attack east of Damascus last week.

High level officials from both sides of the Atlantic, the US Vice President Joe Biden and David Cameron among them, have stressed that they have little doubt that the intelligence proves the regime’s culpability for the attack, which left hundreds of dead in an area of rebel control.

The evidence to support those claims is being compiled by the Director of National Intelligence in the US, according to the Washington Post, and is due to be released in the coming days. But some details about what it may contain have already been leaked.

The main body of evidence is said to comprise of intercepted communications between Syrian military units on 21 August, the day of the attack, and the movement of chemical weapons in advance to the Damascus suburb where the attack took place.

The information regarding the movement of chemical weapons was delivered by the Israeli intelligence services to the CIA, which then verified the information, according to a report in the Wall Street Journal that cites Arab officials.

The intelligence gleaned from intercepted communications was leaked by a “US intelligence official” to Foreign Policy magazine’s The Cable blog. According to the report, it consists of communications between an official at the Syrian Ministry of Defence and the leader of a chemical weapons unit.

The two people “exchanged panicked phone calls,” the intelligence official told The Cable. The Syrian Ministry of Defence official reportedly demanded answers from the head of the chemical weapons team following the alleged nerve agent strike in Ghouta.

If that account of the exchange is accurate, it may be the case that the attack was carried out without the knowledge of Assad’s inner circle.

"It's unclear where control lies," one US intelligence official told The Cable. "Is there just some sort of general blessing to use these things? Or are there explicit orders for each attack?"

“We don't know exactly why it happened," the intelligence official added. "We just know it was pretty fucking stupid."

That intelligence, together with eyewitness reports from doctors who treated victims of the attack and victims themselves, is thought to make up the bulk of the case against the Syrian government, and is likely to be presented as justification for any military attack.

Officials in the US and the UK have made it clear that any decision to proceed with military action will be based on intelligence gathered by the US, and not the findings brought back by the UN inspectors currently on the ground in Syria.

A day before the inspectors were able to visit the site of the attack in Ghouta, east of Damascus, the foreign secretary William Hague said that it was “clear” the Syrian regime was behind the attack.

On Tuesday, White House spokesman Jay Carney said of the inspectors that he was “not sure they need to fulfill their mandate" because the evidence was already conclusive.

Syria and its allies in Russia and Iran have denied that the Syrian government was behind the attack, and instead have suggested that rebels fighting to remove Assad from power are responsible.

On Monday, Mr Cameron spoke to the Russian President Vladimir Putin, who said there was no evidence yet that Syria had used chemical weapons against rebels. Similarly, the official Chinese news agency, Xinhua, said Western powers were rushing to conclusions about who may have used chemical weapons in Syria before UN inspectors had completed their investigation.

The Obama administration has indicated that it will make the intelligence proving the Syrian government’s culpability public in the coming days.