The team were originally scheduled to depart Syria on Sunday, but will now leave on Saturday, only a short time after visiting the site of the alleged chemical weapons attack said to have taken place in a Damascus suburb on August 21.
The inspectors visited the site in the Eastern Ghouta district of the capital earlier this week, and interviewed witnesses and took samples from the scene of the alleged attack, which reportedly killed hundreds of civilians.
Speaking in Vienna, Ban said the inspection team “will continue investigation activities until tomorrow, Friday, and will come out of Syria by Saturday morning and will report to me.”
Under the terms of their mandate, the inspectors are tasked with determining if chemical weapons were used, but not which side is responsible for using them.
Earlier this week, the governments of the US, UK and France accused the Syrian government of the attack, and said that chemical weapons, possibly sarin nerve gas, had been used. They also said that they were considering launching military strikes to deter further use of chemical weapons in the conflict.
In recent days, leaders and officials from the US, UK and France said that no decision has been taken to attack, although plans and measures were in place to do so, following domestic and international pressure to wait until the results of the UN investigation are known.
Analysts say that the three states are unlikely to win Security Council approval for military strikes on Syria as things currently stand, given the disapproval of Russia and China, permanent members of the Security Council, of Western intervention in the conflict.
In the UK, the British government published legal advice that said the UK and its allies could act to prevent humanitarian tragedies in Syria without UN authorization if the Security Council was deadlocked.
However, Prime Minister David Cameron was challenged by the opposition Labour Party on a parliamentary motion approving military action in Syria, with Labour calling on the government to wait for the results of the UN investigation and for “compelling evidence” of the Syrian’s government’s responsibility for the attack to emerge before taking action.
Speaking in parliament on Thursday in an emergency debate, Cameron appeared to offer a number of concessions on the issue. He said: “It is this house that will decide what steps we next take. If you agree to the motion I have set down no action can be taken until we have heard from the UN weapons inspectors, until there has been further action at the United Nations and another vote in this house.”
In the US, the secretaries of defense and state, Chuck Hagel and John Kerry respectively, are scheduled to brief congressional leaders on Thursday evening, together with National Security Advisor Susan Rice and Director of National Intelligence James Clapper.
They are expected to discuss the evidence from official US government reports that the Syrian government is responsible for the August 21 attack, though press reports say that some doubts still remain within the US intelligence services on some specific details.