Russian Federation said a U.S. military strike against Syria would have "grave repercussions" and stressed that the use of chlorine or sarin had not been confirmed in the attack Saturday in Douma.
The attacks come during an uneasy time in Syria, and also as President Trump carefully navigates exactly what to do in the country, where there are approximately 2,000 USA troops now stationed.
Haley said those responsible for the attacks were "monsters", adding: "We must not overlook Russian Federation and Iran's roles in enabling the Assad regime's murderous destruction".
Britain and the United States agreed on Monday that the attack bore the hallmarks of previous chemical weapons attacks by Assad's government, but neither country gave details of what kind of chemical might have been used or how the attack was staged.
The supposed poison gas attack killed at least 80, leaving men, women and children foaming at the mouth and struggling to breathe in the rebel-held town of Douma, a suburb of Damascus.
Syrian government forces had launched an air and ground assault on Douma, the last town held by rebels in eastern Ghouta, on Friday.
"Through the relevant channels we already conveyed to the USA that armed force under mendacious pretext against Syria - where, at the request of the legitimate government of a country, Russian troops have been deployed - could lead to grave repercussions", he said.
Both the Joint Chiefs of Staff and CENTCOM, the USA forces in the Middle East, were compiling target lists and attack options to be presented to Trump and his national security team within hours, the officials said. The Pentagon denies launching airstrikes on Syria.
Then, within days the United States military fired cruise missiles at a Syrian airfield where the sarin attack had been launched from.
The attacks have come almost a week after Trump expressed his desire to bring the USA troops back to the country.
Trump has declared his intent to withdraw US troops from Syria in the coming months, despite resistance from many of his advisers.
The U.S. ambassador to the United Nations, Nikki Haley, urged joint action against Syria at a meeting of the UN Security Council on April 9, but vowed that the United States would act on its own if the UN didn't respond.
"The Secretary-General is particularly alarmed by allegations that chemical weapons have been used against civilian populations in Douma", a spokesman for U.N. Secretary-General Antonio Guterres said in a statement. "The great evil of chemical-weapons use that once unified the world in opposition is on the verge of becoming the new normal".
The stakes are higher for any new USA military action, with Trump explicitly mentioning Iran and Russian Federation in connection with the weekend attack.
The UN Security Council was holding an emergency meeting today to discuss the chemical attack.
Israel is said to have carried out around 200 airstrikes on Hezbollah and Syrian targets inside Syria since the start of the war, according to The New Yorker's Robin Wright. "However, we continue to closely watch the situation and support the ongoing diplomatic efforts to hold those who use chemical weapons, in Syria and otherwise, accountable". Defense analysts quoted by Reuters said there were deployments of Russian forces at the base.
Iranian President says U.S. will regret if it scraps n
But it is still allowed to develop nuclear technology for civilian purposes, including energy production and scientific research. Trump has argued behind the scenes that the nuclear deal makes the United States look weak, a senior USA official said.
India committed to help in development of Nepal: PM Modi
We have developed our friendship according to time with a objective to eradicate poverty, improve living standards. Oli was at odds with India when he previously served as prime minister, and tried to build ties with China.