The Syrian Observatory for Human Rights, a British-based war monitor, also said pro-Syrian government forces were emptying main airports and military airbases.
Later, during an afternoon event in the White House Rose Garden at which Trump touted an increased defense budget, the president declared that "we're going to have the strongest military we've ever had, and can you think of a better time to have it?"
"We continue to consider it extremely important to avoid any steps that could lead to more tension in Syria", Mr Peskov said.
Russian Federation has warned the United States that launching air strikes in response to a suspected chemical attack in Syria could spark a war between the two countries.
"We hope that there will be no point of no return - that the USA and their allies will refrain from military action against a sovereign state".
May recalled ministers from their Easter holiday to debate action over what she has cast as a barbaric poison gas attack by Syrian government forces on civilians in the formerly rebel-controlled town of Douma, just east of the capital Damascus.
He has said that any French strikes would target the Syrian government's chemical facilities and has spoken at length with Trump since Sunday, after the first reports of a possible chemical attack in Syria emerged.
Justin Bronk, an air-combat expert at the Royal United Services Institute, said chemical weapons killed fewer people than regular bombs but did so in a "particularly terrifying" way.
He said even if the investigative team verifies the use of chemical weapons, "we will not know who did it". Earlier on Thursday, the Russian ambassador to the United Nations, Vassily Nebenzia, said that he believes any strike against Syria would violate the UN charter.
But Obama adviser Frederic Hof believes it's up to Trump to lead in Syria by staying the course in a complex conflict that implicates the entire Middle East and Russian Federation - another Assad supporter.
Fans greet Oklahoma City Thunder at airport after clinching playoff spot
San Antonio improved to 33-8 at home this season and now hold the No. 5 seed in the West due to tiebreakers over the Thunder. The final National Basketball Association playoff spot will be decided on the final day of the regular season.
Which ships, aircraft, missiles and troops will be used against Syria?
The US confirmed on Thursday that the Assad regime was moving air assets to Russian airbases to avoid strikes. A USA guided-missile destroyer, the USS Donald Cook, is in the Mediterranean.
Mr Trump reinforced his threat of military action in a tweet on Wednesday, stating: "Russia vows to shoot down any and all missiles fired at Syria".
The drumbeat of military action appeared to grow louder, as Russian Federation stonewalled diplomatic efforts at the United Nations and France declared "proof" that Moscow's Syrian ally carried out a deadly chemical weapons attack that killed more than 40 Syrians.
"They are the guarantors of law and order in the town", RIA news agency quoted Russia's Defence Ministry as saying.
"Any possible action will only cause more instability in the region and threaten worldwide security and peace", Syrian state TV quoted Assad as saying at a meeting Thursday with a high-level Iranian delegation in Damascus.
The Syrian conflict has increasingly widened the rifts between Moscow, Washington and European powers, and inflamed the bitter rivalries that run across the Middle East. France is already involved in the US -led coalition created in 2014 to fight the Islamic State group in Syria and Iraq.
There is no guarantee lawmakers would rubber-stamp a decision for military strikes.
The UK has since ordered the Royal Navy to move its submarines within missile range of Syria, and Tornado jets were pictured being re-fuelled at RAF Marham in Norfolk ahead of potentially being deployed to join other RAF colleagues at a base in Cyprus.
Trump spoke by phone with British Prime Minister Theresa May. Israel has said it won't let Iran entrench militarily in Syria, and Prime Minister Benjamin Netanyahu took the occasion of Israel's Holocaust Remembrance Day to warn Tehran not to test his country.
"Never said when an attack on Syria would take place". She would not seek approval from parliament, the BBC said.