United States Secretary of State John Kerry has laid the groundwork for possible military action against the Syrian Government, in response to last week's apparent chemical weapons attack.
Mr Kerry says there is little doubt poisonous gas was used against civilians in rebel-held suburbs of Damascus, and that forces loyal to Syrian President Bashar al-Assad were responsible.
Mr Kerry says the evidence so far leaves little doubt there has been a large scale chemical attack.
"This is about the large scale, indiscriminate use of weapons that the civilised world long ago decided must never be used at all," he says.
Mr Kerry says the attack should "shock the conscience of the world", and all nations must work to ensure chemical weapons are never used again.
"The indiscriminate slaughter of civilians, the killing of women and children and innocent bystanders by chemical weapons is a moral obscenity," he says.
"By any standard it is inexcusable and despite the excuses and equivocations that some have manufactured it is undeniable."
He said US President Barack Obama believes there must be accountability for those who would use the world's most heinous weapons against the world's most vulnerable people.
Mr Kerry's strongly worded speech signals the United States is indeed preparing some kind of military response to events in Syria.
It came hours after weapons inspectors visited one of the attack sites to interview and take blood samples from victims.
United Nations investigators crossed the front line from the centre of the capital, which remains under government control, to inspect the Mouadamiya suburb, one of at least four neighbourhoods hit by poison gas.
The UN says one vehicle in its convoy was crippled by shooting by unidentified snipers but mentioned no injuries.
The convoy continued on after turning back for a replacement car.
The inspectors are reported to have examined victims being treated at a makeshift hospital and taken blood samples from them.
Video filmed at the site shows inspectors in black and blue body armour and blue UN helmets walking through a street as curious onlookers came up to watch.
The inspectors later returned to their hotel, and within an hour residents reported that the shelling of Mouadamiya resumed.
UN secretary general Ban Ki-moon has praised the team for doing their job in very dangerous circumstances and says he is waiting for the team's first report.
