After Russia announced on Monday that it would soon supply its advanced S-300 missile systems to Syria, the Trump administration was quick to join Israel in expressing its objection.

“We think introducing the S-300s to the Syrian government would be a significant escalation by the Russians,” US national security adviser John Bolton said on Monday, adding, “and something that we hope, if these press reports are accurate, they would reconsider.”

Bolton gave several headline-worthy quotes, sounding the alarm about Iranian military involvement in Syria.

“There shouldn’t be any misunderstanding here…. The party responsible for the attacks in Syria and Lebanon and really the party responsible for the shooting down of the Russian plane is Iran,” he claimed.

“We’re not going to leave as long as Iranian troops are outside Iranian borders, and that includes Iranian proxies and militias,” he added.

President Donald Trump’s top adviser on national security matters also reiterated his warning that any future chemical-weapons attack attributed to the Syrian military – a basis already cited twice for recent US air strikes on Syria – would be met with a harsh response.

“If in fact they make the mistake of using chemical weapons again, the retaliation would be much stronger than before and would have the intended effect of creating structures of deterrence that they never do it again,” Bolton warned.

Israel has been vocal in its opposition to deployment of the S-300 missile systems in Syria, warning that it would strike the defenses if they were used against Israeli forces.

“One thing should be clear – if someone fires on our planes, we will destroy them,” Israeli Defense Minister Avigdor Lieberman was reported as saying last April. “What’s important to us is that the weapons defense systems that the Russians transfer to Syria are not used against us. If they are used against us, we will act against them.”

Moscow had said that Israel would suffer “catastrophic consequences” if it targeted the equipment.

After the recent downing of a Russian aircraft over Syria, speculation has swirled that an increasingly close and publicly warm relationship between Russian President Vladimir Putin and Israeli Prime Minister Benjamin Netanyahu is in jeopardy. Russia blamed Israel for the incident, which led to the deaths of more than a dozen Russian airmen. Israel said its aircraft were not responsible for the strike, which it said was conducted by Syrian forces, using Russian-made weapons.