Top-level Israeli security officials met on Wednesday to prepare for scenarios in which Israel is attacked by Syria or Iran, following a tweet by U.S. President Donald Trump declaring that he would bomb Syria.

Iran, which has been operating militarily in Syria and backs Syrian President Bashar Assad, has threatened to respond to an Israeli airstrike on the T-4 air base in Syria on Monday.

Syria and Russia have blamed Israel for the attack, which has similarly been confirmed by the United States. Israel has neither confirmed nor denied performing the operation.

On Saturday, a chemical-weapons attack in the rebel-held Syrian town of Douma was blamed on Syrian President Bashar Assad. Syria and Russia denied the attack.

In response, Trump tweeted that while Russia vowed to protect Syria against attack, “Get ready Russia, because [attacks] will be coming, nice and new and ‘smart!’ You shouldn’t be partners with a Gas Killing Animal who kills his people and enjoys it!”

The tweet, followed an appearance by Russia’s ambassador to Syrian-allied Lebanon, who told the Hezbollah-run television network Al-Manar that U.S. missiles would be shot down by Russia, “as well as the sources they were fired from.”

British Prime Minister Theresa May called an emergency cabinet meeting on Thursday, with reports indicating that she has already ordered submarines to move within missile range of Syria.

U.N. Security Council Secretary General António Guterres stated that he was in touch with the ambassadors of the five Permanent Members of the Security Council to “reiterate my deep concern about the risks of the current impasse and stressed the need to avoid the situation spiraling out of control.”

Since the alleged chemical-weapons attack, Moscow has announced that Douma is “totally stabilized” and will be patrolled by Russian military police.