U.S. Ambassador Nikki Haley told the council that a cease-fire resolution it adopted two weeks ago had failed and that the new resolution "provides no room for evasion".
U.N. Secretary-General António Guterres said the bombings in Ghouta have only gotten worse since the Security Council called for the ceasefire, noting that the Syrian government - helped by Russian Federation and China - has significantly increased its controlled territory in the region.
Haley also warned Syria that the United States was prepared to take military action for alleged chemical attacks that are killing and wounding Syrian civilians.
Haley described Russian Federation and Syria's continued subversion of a peace process a "mockery", and concluded her speech with a warning, and recalled the US's April 7, 2017, naval strike on Syrian air bases thought to have participated in a sarin gas attack on its own people. "But it is a path we have demonstrated we will take, and we are prepared to take again".
"Syria is Russia's. They took ownership of it, they need to fix it and now they're whining because they can't", Haley said during her Central America trip.
"We have seen nothing but carnage in response to the Security Council's resolution calling for a halt to the massacre in Eastern Ghouta", says Arnaud Quemin, the Mercy Corps director of programs in Syria.
The Trump administration frequently points to the de-escalation zone as a sign of progress it can achieve with Moscow on reducing the violence in Syria.
"We urge all parties in the southwest de-escalation zone not to take actions that would jeopardize the ceasefire and make future cooperation more hard".
Air strikes and rocket fire slammed into the towns of Harasta and Arbin, the Britain-based monitor said, as the regime used the recently recaptured town of Medeira nearby as a launching pad for a ground assault. It is not even safe to put chickens in. As many as 300 people may be packed into a shelter, with no bathroom and just one toilet.
Douma residents said dozens of people were trapped alive under rubble, with rescuers unable to reach them due to the intensity of the raids.
Home to some 400,000 civilian residents, Eastern Ghouta has remained the target of a crippling siege by the Syrian regime - of which Russian Federation is a major ally - for the last five years.
The civilians used a corridor established by the Syrian army amid military gains that have effectively divided eastern Ghouta into three parts.
State television broadcasts from the government-controlled side of the battlefront showed dark grey clouds of smoke billowing from several places across a landscape of shattered buildings.
UNICEF says no fewer than 1.5 million people have suffered permanent physical or psychological injuries in Syria's seven-year war.
It has confirmed the deaths of 511,000 people, it said, and has the names of more than 350,000 of them.
Syria's conflict broke out in March 2011 with peaceful protests against Assad, but a regime crackdown paved the way for a fully-fledged war. About 85 percent were killed by government forces and their allies, it said.
The United Nations has warned of dire shortages of food and medicine, where global deliveries have always been erratic and often obstructed before they could reach the enclave. It would also be the worst setback for rebels since the opposition was ousted from the eastern half of the city of Aleppo in late 2016 following a similar siege and bombing campaign.