WASHINGTON (CBSNewYork) — President Donald Trump told Russia to “get ready” Wednesday, saying missiles “will be coming” to Syria following a suspected chemical attack.

The president issued the warning on Twitter.

“Russia vows to shoot down any and all missiles fired at Syria. Get ready Russia, because they will be coming,” Trump said. “You shouldn’t be partners with a Gas Killing Animal who kills his people and enjoys it!”

In a second tweet, the president said “our relationship with Russia is worse now than it has ever been, and that includes the Cold War.”

“There is no reason for this. Russia needs us to help with their economy, something that would be very easy to do, and we need all nations to work together,” he said. “Stop the arms race?”

U.S. ships have moved into place in anticipation of orders from the president, and now it appears Great Britain has moved closer to committing to possible allied military action, CBS2’s Dick Brennan reported.

“We are still assessing the intelligence, ourselves and our allies, we are still working on this,” Defense Secretary James Mattis said.

“All the indications are that the Syrian regime was responsible, and we’ll be working with our closest allies to consider how we can ensure that those responsible are held to account,” UK Prime Minister Theresa May said. 

The Kremlin earlier Wednesday urged countries to avoid taking action that could further destabilize war-torn Syria, CBS News reported.

“As before we would hope that all sides will avoid steps that in reality are not provoked by anything and that could destabilize the already fragile situation in the region,” Kremlin spokesman Dmitry Peskov said.

On Monday, Trump told reporters during a Cabinet meeting the administration would be making “major” decisions on Syria within the next 24 to 48 hours.

“This is about humanity, we’re talking about humanity, and it can’t be allowed to happen,” he said. “We cannot allow atrocities like that.”

Mattis also said Monday that he would not “rule out anything” as a response against Syrian President Bashar Assad. The president also said that “nothing’s off the table.”

Syria and its allies have denied all responsibility for the alleged gas attack, which rebel leaders say killed dozens of people. Russia also said it has visited the sight of the alleged attack and said it found no evidence to support the claims.