Syrian ceasefire wins UN Security Council approval after a week of delays while hundreds of civilians died The U.N. Security Council voted unanimously to adopt a temporary ceasefire.

 -- The United Nations Security Council voted unanimously today to adopt a resolution demanding a temporary humanitarian ceasefire across war-torn Syria, a measure that was delayed several times this week while hundreds of civilians died in airstrikes by the Syrian government and its allies.

The resolution demands all parties to cease hostilities in Syria for 30 days to deliver much-needed humanitarian aid and to evacuate the sick and wounded. It calls for the ceasefire to begin "without delay."

One exemption to the ceasefire is allowed under the resolution -- attacks on militants from ISIS and any Al Qaeda affiliates.

"We are late to this crisis -- very late," U.S. Ambassador to the U.N. Nikki Haley said after the vote inside the Security Council chambers at the U.N. headquarters in New York City.

The Syrian government, with support from Russia and Iran-backed militants, has carried out a fierce military offensive this week against the last major territory still under rebel control. Since Sunday night, the bombing campaign has killed at least 462 civilians, including 103 children, and wounded more than 2,000 people in the rebel-held enclave of Eastern Ghouta, according to the Syrian Observatory for Human Rights, a United Kingdom-based monitoring group. It’s among the deadliest offensives of Syria's seven-year civil war.

Syria's Ambassador to the U.N. Bashar Jaafari, who was present for today's vote, defended the military offensive in Eastern Ghouta and criticized those who don't want his government combating "terrorists" on its own territory.

“We have responsibilities as a state to protect our citizens," Jaafari said in Arabic through a translator, following the vote. "We are exercising our right to fight terrorism."

The vote on the resolution had been scheduled and delayed three times this week amid lengthy, drawn-out negotiations. Russia's Ambassador to the U.N. Vassily Nebenzia had repeatedly called an immediate ceasefire unrealistic.

Sweden's Ambassador to the U.N. Olof Skoog said the resolution could potentially abate violence and save lives.

“The U.N. convoys and evacuation teams are ready to go,” Skoog said prior to today's vote.

Following the unanimous vote, Haley took the floor to lambaste Russia for stalling the vote. She said the Russian ambassador "obstructed the vote" and "dragged out" negotiations this week, which she said cost lives.

"At least 19 health facilities have been bombed since Sunday," Haley said. "How many mothers lost their kids to the bombing and the shelling?"

Haley and other Security Council members acknowledged the resolution "will be tested" and that all parties "must rise to the challenge of maintaining the ceasefire." Previous truces haven't been successful in ending fighting in Syria.

Council members also expressed concern that Syrian President Bashar al-Assad's regime will not adhere to the immediate ceasefire. Still, Haley said, "we must demand nothing less."

"We owe this to the innocent people of Syria begging for help," she said.

What started as a local protest movement in Syria’s southern city of Dara'a expanded into a full-fledged civil war by 2012. ISIS, which grew out of Al Qaeda in Iraq, took root in northern and eastern Syria in 2013 after seizing swaths of territory in neighboring Iraq. The jihadist group is fighting to overthrow Assad's regime and establish a caliphate.

The Syrian Civil War has pulled in the United States, Russia, Iran and almost all of Syria's neighbors. It has become the largest humanitarian crisis since World War II, according to the U.N.

Earlier this week, while speaking at a Security Council meeting, U.N. Secretary-General Antonio Guterres urged an immediate suspension of "all war activities" in besieged Eastern Ghouta, where he said 400,000 people are "living in hell on earth."

Since late December, there has been an upsurge in violence in the rebel-held enclave, located just outside the Syrian capital Damascus. The residents trapped there have little access to food, water, fuel, electricity and health care.

“A human tragedy is unfolding in front of our eyes," said Guterres, explaining that an estimated 700 people in Eastern Ghouta need urgent medical treatment that cannot be provided there.

“I don’t think we can let things go on in this horrendous way," he said.