Walid Moualem, the Syrian foreign minister, has 'categorically' denied that his country was using chemical weapons on its own people.

At a press conference held in Syrian capital Damascus on Tuesday, he challenged the world to provide evidence that the Syrian government was behind last week's alleged chemical weapons attack in eastern Ghouta, a suburb of the capital Damascus.

The Syrian foreign minister accused John Kerry, his American counterpart, of lying and disregarding the work of UN inspectors when he stated there was “undeniable" evidence of a large-scale chemical attack.

"We are all hearing the drums of war being beaten around us. If these countries are willing to launch an aggression or military act against Syria, I believe, the pretext of chemical weapons is false, baseless and groundless. And as I said, I challenge, I dare them to produce any single piece of evidence", Moulem said.

He also claimed that the second trip of the UN inspectors to the site of an alleged chemical weapons attack

had been postponed to Wednesday due to disputes among the rebels.

The Syrian foreign minister said the rebels in eastern Ghouta could not reach agreement about guaranteeing the team's safety.

"A comprehensive assessment determined that the visit should be postponed by one day in order to improve preparedness and safety for the team", the UN announced in a statement released just after Moualem's press conference.

The UN inspectors were due to begin a second day of investigation into last week's alleged chemical-weapons attack in the suburbs of the Syrian capital, Damascus.

The Syrian opposition says more than 1,300 people died when toxic gases were unleashed on Eastern Ghouta and Moadamiya - two neighbourhoods on the outskirts of Damascus - last Wednesday.

The UN team came under sniper fire on Monday as they tried to visit an area in western Damascus.

The convoy of six vehicles was shot in the buffer zone between rebel and government areas near Damascus as it travelled to Moadamiya and Ghouta.