He will remain in Washington to "oversee the American response to Syria", the White House said.
"There was no chemical weapons attack".
Nebenzya noted that over the weekend, when Douma was allegedly targeted by chemical weapons, the United States side declared it already knew who was at fault - "Animal Assad", Russia and Iran - so the USA proposal appeared insincere.
The Organisation for the Prohibition of Chemical Weapons said Syria has been asked to "make the necessary arrangements for such a deployment".
All of this comes after President Trump tweeted Sunday that "Russia and Iran" were responsible for the chemical attack and wared there would be a big price to pay. President Trump has said the US will respond "forcefully" once responsibility for the attack is established.
Meanwhile, Russian Foreign Minister Sergei Lavrov said on April 10 that Moscow will propose a UN Security Council resolution calling for an investigation by the OCPW into the attack.
U.S. Ambassador to the United Nations Nikki Haley (R, Front) and British Ambassador to the UN Karen Pierce (L, Front) vote in favor of a U.S. -drafted resolution on probe of chemical weapons use in Syria at the UN headquarters in NY, on April 10, 2018.
Will there be a military strike?
Trump has pledged a "forceful" response, and has spoken of numerous military options.
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France said it will retaliate against the regime of the Syrian president if evidence emerges that it was behind the attack, a government spokesman said.
It's unclear if there's an appetite for broader sanctions against Venezuela, but the region did take the extraordinary step of rescinding President Nicolás Maduro's invitation to this year's event.
"Any confirmed use of chemical weapons, by any party to the conflict and under any circumstances, is abhorrent and a clear violation of global law", Secretary-General Antonio Guterres said in a statement. According to BBC, Mr Trump said the USA was getting some "good clarity" on who was responsible for the incident in Douma on Saturday.
Tensions come roughly a year after the USA launched 59 Tomahawk missiles at Syria after it used chemical weapons on another rebel-held city.
Neither the death toll nor what exactly occurred can be verified as the area is blocked off, with access denied.
U.S. Ambassador Nikki Haley told the Security Council on Monday that both Russian Federation and Iran could stop the Syrian government's "murderous destruction", adding that Moscow's hands are "covered in the blood of Syrian children".
More than 133,000 people have fled a suburb of the Syrian capital, Damascus, in the face of the government's military onslaught, the United Nations refugee agency said Tuesday.
It said this included breathing difficulties, bluish skin, mouth foaming, corneal burns and "the emission of chlorine-like odour".
As many as 150 people were reported dead with 1,000 more injured from the suspected chemical weapon attack.