USA officials told NBC and CNN that the Washington now "has blood and urine samples" from the reported chemical weapons attack that suggest "the presence of both chlorine gas and an unnamed nerve agent", two officials said.
Other countries, including Britain and France, are also likely to support US military action in which the principal aim will be disabling the regime's chemical weapons.
The U.N. Security Council has rejected a Russian resolution calling for condemnation of the "aggression" by the United States and its allies against Syria.
Haley said the main difference between the US-drafted text and the Russian one is that Russia wanted to choose the investigators and assess the outcome while the USA text allows for an independent investigation.
Russian officials and President Trump have US have exchanged heated rhetoric since Trump began talk of a USA response to the alleged chemical attack throughout the past week.
The US, UK and France launched coordinated strikes against three Syrian sites in retaliation for the an alleged chemical weapons attack on civilians in the last rebel stronghold of Douma, leaving at least 49 people dead.
Doctors and witnesses have said victims showed symptoms of poisoning, possibly by a nerve agent, and reported the smell of chlorine gas.
The U.S. draft had the overwhelming support of the council with 12 members of the 15-member council voting in favor, and only two - Russian Federation and Bolivia - voting against.
Moving to return to diplomacy, France said it was working with the United States and Britain on a draft resolution that would address chemical weapons use, the humanitarian crisis and the future of the peace process in Syria.
On Thursday, Mrs May gained cabinet approval for an "international response" in Syria and Mr Macron said his government has proof that the Assad regime used chemical weapons in Douma.
The Federal Aviation Administration has prohibited US airlines or foreign airlines flying with a USA certificate from flying over Syria since at least 2014 because of anti-aircraft weapons controlled by non-state actors, threats made by extremist groups and ongoing military fighting. The first one is the draft resolution on setting up a United Nations mechanism to investigate chemical attacks in Syria.
France and Britain discussed with the Trump administration how to respond to the Douma attack.
"Syria is keen on cooperating with the OPCW to uncover the truth behind the allegations that some Western sides have been advertising to justify their aggressive intentions", Syria's state news agency SANA said.
If the United States action follows the pattern of a previous punitive strike on Syria past year, it will begin with a salvo of cruise missiles fired from American warships in the Mediterranean, as Trump implied when he tweeted they would be "nice, new and "smart". The use of chemical weapons in Syria dropped off significantly afterward.
Nebenzia warned against any USA military action, saying that armed force "under mendacious pretext" and with Russian troops in Syria, "could lead to grave repercussions".
Russian Federation vetoed a USA -drafted resolution to create a new inquiry to ascertain blame for such attacks.
European airspace authorities are warning aircraft to be careful over the next days when flying close to Syria because of possible military action against President Bashar Assad's forces.
"While Russia was busy protecting the regime, Assad took notice", she said. May "on the need to take action and deter the further use of chemical weapons".