“Our experts are still on the ground investigating the use of chemical weapons,” Mr. Ban told journalists at Vienna City Hall, adding that the investigation team will continue its activities until tomorrow, leave Syria by Saturday morning and then inform him as soon as they are out.

The team led by Swedish scientist Dr. Ake Sellstrom, has been carrying out its work without incident following a pause in the investigation Tuesday, when its convoy was attacked by snipers while heading to the Damascus suburb of Ghouta, where chemical weapons were allegedly used on 21 August.

The shortened visit means the UN chief will not participate in the UN European Alpbach Forum, which will now be chaired by President Jose Manuel Barroso of the European Union.

Earlier today, Mr. Ban said he spoke by phone with United States President Barack Obama about how the United Nations, the US and the world can work together, as well as “how we can expedite the process of the investigation.”

Mr. Ban said he expressed his wish that the investigation team should be allowed to continue their work as mandated by the Member States to probe the alleged use of chemical weapons by the Government at Khan al-Asal and other claims.

“I told him that we will surely share the information and the analysis of samples and evidence with Members of the Security Council and UN members in general,” Mr. Ban said.

Also today, Mr. Ban discussed the investigation and the overall situation in Syria with Austrian President Heinz Fischer and Chancellor Werner Faymann.

“We are of the opinion that the situation should be resolved in a peaceful way through dialogue,” he told journalists after the meetings.

Mr. Ban and other senior UN officials, including Joint Special Representative of the UN and the League of Arab States Lakhdar Brahimi, have repeatedly urged pursuing all diplomatic options to bring the Syrian parties to the negotiating table, and stressed there is no military solution to the crisis.

In a joint press encounter last night with Minister of Foreign Affairs Frans Timmermans in the Netherlands, Mr. Ban said that his responsibility and mandate were “to conduct a thorough and complete investigation” of the allegations of chemical weapons use in Syria and any actions on a response would be deemed by the Security Council.

In response to speculation that the West is planning to take military action, Mr. Ban said he would not speculate on anything on which he is not aware, adding, “If there needs to be any such unilateral or military actions… as Secretary-General I would like to emphasize that it is the Charter that provides the framework for action to ensure international peace and security.”

Meanwhile, British lawmakers on Thursday voted against military intervention in Syria, in a major setback for both British Prime Minister David Cameron and the Obama administration in their push to punish the Assad regime for an alleged chemical weapons strike.  The measure was defeated, by 285 votes to 272 votes.

The outcome raises serious questions for Obama, who has not yet made a decision on the way forward in Syria but had indicated his administration would need international support for any strike.

Mr. Ban has reiterated that the use of chemical weapons by anyone, for any reason, under any circumstances are crimes against humanity and that must be held accountable.

“We have been very clear to the Assad regime, but also to other players on the ground, that a red line for us is if we start seeing a whole bunch of chemical weapons moving around or being utilized. That would change my calculus,” Obama said.

“That would change my equation. . . . We’re monitoring that situation very carefully. We have put together a range of contingency plans.”

Last month, Syria acknowledged for the first time that it had chemical weapons and said it could use them if foreign countries intervened in their affairs. The threat drew strong warnings from Washington and its allies.

“We cannot have a situation where chemical or biological weapons are falling into the hands of the wrong people,” Obama told the impromptu news conference on Monday admitting he was not “absolutely confident” the stockpile was secure.

Western countries and Israel have voiced fears that chemical weapons could fall into the hands of militant groups such as Lebanese Hezbollah Syrian President Bashar al-Assad.

Israeli Defense Minister Ehud Barak has previously voiced fears that chemical weapons could fall into hands of militant groups and has warned that it would take military action, if needed, to ensure those weapons did not reach Assad’s Hezbollah allies in Lebanon.

The US president’s comments came as a female Japanese reporter was killed while covering clashes in the city of Aleppo, according to the Washington Post. 

The dead reporter was 45-year-old Mika Yamamoto, was the fourth foreign reporter killed in Syria since March 2011.

Meanwhile, the UK-based Syrian Observatory for Human Rights  said more than 140 people were killed in Syria on Monday.

The opposition Syrian National Council said that government forces using combat helicopters, tanks and heavy artillery had carried out “savage” attacks on Herak, south of Damascus, warning that food and medicines were running out, according to Al Jazeera.

23,000 people have now been killed since March last year, according to the Observatory, while the UN puts the death toll at  17,000.

Friday’s massacre of more than 100 civilians, many of them children, in Houla has brought widespread criticism and triggered calls for the West to take more robust action in Syria, despite Russian and Chinese opposition.

Clinton on her first stop on a  European tour, in remarks to Danish students,  Clinton said every day of slaughter in Syria was increasing the case for tougher international action. She explained why Libya was different than Syria, where Western-led air strikes last year helped bring an end to Muammar Qaddafi’s rule.

 Clinton said Syria had a more diverse society with greater ethnic divisions, no unified opposition, stronger air defenses and a much more capable military than Libya’s, Reuters reported.

Russia’s continued support for Assad “is going to help contribute to a civil war,” Clinton warned, according to Al Arabiya.

Clinton did not give any alternatives to United Nations-Arab League envoy Kofi Annan’s efforts to try to halt the crisis in Syria.

The Houla massacre and the discovery of new execution-style killing since then has raised the pressure for international action.

Meanwhile, Syrian rebels yesterday  warned they will resume their defense of civilians if the government does not return to the peace plan by Friday.

The Syrian regime on Thursday blamed the Houla massacreon anti-government armed groups.