"We have reached the moment when the world must see justice done", Haley told an emergency meeting at United Nations headquarters in NY.
"We are making a decision as to what we do with respect to the frightful attack that was made near Damascus, and it will be met forcefully, and when I'm not saying because I don't like to talk about timing".
Both Damascus and Moscow had warned against using the allegations to justify military action against Assad.
But Russia says it can not support the proposal because it contains "unacceptable elements".
"We have reached the moment when the world must see justice done", Haley told the council.
President Bashar al-Assad's government and Russian Federation, his most powerful ally, said there was no evidence that a gas attack had taken place and the claim was bogus.
She added: "Meetings are ongoing".
Assad regime forces struck targets in Eastern Ghouta's Douma district on Saturday midnight, using a toxic gas which left at least 78 civilians dead, according to Syrian Civil Defense, also known as the White Helmets.
"Russia will inevitably veto the USA resolution criticizing Assad, and Washington will use this to justify military strikes", he said.
"We can't let that happen".
Mrs May sidestepped a question on whether Parliament would be recalled from recess to debate any military intervention.
The White House, Pentagon and State Department declined to comment on specific options or whether military action was likely.
"The timing of the strike isn't coincidental", said Michael Horowitz, a senior analyst at Le Beck International, a Middle East-based geopolitical and security consultancy. Monday was the first day on the job for Trump's new national security adviser, John Bolton, who has previously advocated military action against Syria.
When asked if Putin himself might be responsible for the attacks, Trump responded that the Russian president would pay the price if he was involved in the use of chemical weapons.
Haley accused Russian Federation of protecting Syria at the United Nations while Moscow's military advisers in Damascus are helping Assad wage a "starve or surrender campaign" against Syrian civilians that includes the use of chemical weapons.
British Prime Minister Theresa May called it "reprehensible" and said if the Assad government was found to be responsible, it would be held to account.
"President Trump last week signaled to the world that the United States would prematurely withdraw from Syria", McCain said in a statement.
Since February 18, Syrian regime forces have been carrying out an offensive against Ghouta that has killed more than 1,700 civilians and cornered rebels in their last holdout of Douma. Both Syria and Russian Federation have denied the Syrian government's involvement in that attack. They said the victims had foam on their mouths. The Syrian-American Medical Society claimed that more than 500 people were brought to medical centers in Eastern Ghouta with symptoms "indicative of exposure to a chemical agent", including breathing problems and bluish skin.
More than 50,000 people, including fighters and their families, are expected to leave Douma, a source involved the negotiations told Reuters earlier on Monday.
RCB vs KKR Live Streaming, IPL 2018 Live Cricket Score
Indian Premier League franchise Kolkata Knight Riders is a team which has one of the biggest fan following in the tournament. Kolkata Knight Riders and Royal Challengers Bangalore are looking forward to lock horns in the third match of IPL 2018 .
BVB besiegt Stuttgart - Frankfurt springt auf Rang vier
Geschäftsführer Hans-Joachim Watzke und Zorc, der seinen Job jüngst bis 2021 verlängert hat, wissen also, was sie zu tun haben. Doch der kühl empfangene Trainer Korkut und Rückkehrer wie Gomez haben Konstanz ins Spiel gebracht.
Chelsea 1-1 West Ham: 5 talking points
While he didn't end up scoring in the game, he was a physical presence winning aerial duels against the West Ham defence. I thought I saw a definite movement with his knee towards Jack". "At least he is positive in what he is doing".
YouTube shooter's bizarre videos key to suspected motive
They identified her as a missing person from the San Diego area, so they notified her family and subsequently released her. Nevertheless, the family said they tried to warn the police that Nasim was angry with YouTube for suppressing her videos.
Wwe Wrestlemania 34 live streaming
Rousey teamed with Kurt Angle against Triple H and Stephanie McMahon , and looked a complete natural in the ring. This has been a match planned for over a year to be the coronation of Reigns as the new "face of the company".