By Steve Holland, Andrew Osborn and Tom Perry

PALM BEACH, Fla./MOSCOW/BEIRUT (Reuters) – Russia warned on Friday that U.S. cruise missile strikes on a Syrian air base could have “extremely serious” consequences, as President Donald Trump’s first major foray into a foreign conflict opened up a rift between Moscow and Washington.

The U.S. military launched dozens of Tomahawk missiles from the USS Porter and USS Ross warships in the Mediterranean Sea that hit the airstrip, aircraft and fuel stations of the Shayrat air base, which the Pentagon says was used to store chemical weapons.

It was Trump’s biggest foreign policy decision since taking office in January and the kind of direct intervention in Syria’s six-year-old civil war that his predecessor Barack Obama avoided.

The American strikes were in reaction to what Washington says was a poison gas attack by the Syrian government of President Bashar al-Assad this week that killed at least 70 people in rebel-held territory.

The U.S. action catapulted Washington into confrontation with Russia, which has military advisers on the ground aiding its close ally Assad.

“We strongly condemn the illegitimate actions by the U.S. The consequences of this for regional and international stability could be extremely serious,” Russia’s deputy U.N. envoy, Vladimir Safronkov, told a meeting of the U.N. Security Council on Friday.

Russian Prime Minister Dmitry Medvedev charged that the U.S. strikes were one step away from clashing with Russia’s military.

Moscow said it had suspended communication with U.S. forces designed to stop planes colliding over Syria, where U.S. jets frequently bomb Islamic States militants. But senior U.S. military officials told Pentagon reporters that Russia has not suspended the military communications channel.

U.S. officials informed Russian forces ahead of the missile strikes, and avoided hitting Russian personnel.

Satellite imagery suggests the Shayrat air base is home to Russian special forces and military helicopters, part of the Kremlin’s effort to help the Syrian government fight Islamic State and other militant groups.

Trump has frequently called for improved relations with Russia which were strained under Obama over Syria, Ukraine and other issues, but the U.S. president said action had to be taken against Assad.

“Years of previous attempts at changing Assad’s behavior have all failed and failed very dramatically,” Trump said as he announced the attack on Thursday night from his Florida resort, Mar-a-Lago, where he was meeting Chinese President Xi Jinping.

“Even beautiful babies were cruelly murdered in this very barbaric attack,” he said, adding: “No child of God should ever suffer such horror.”

ASSAD ‘ON NOTICE’

A wide range of U.S. allies from Asia, Europe and the Middle East expressed support, if sometimes cautiously, for the strikes.

Assad has been “put on notice” by the U.S. action, Britain’s U.N. Ambassador Matthew Rycroft told the Security Council, terming it a “proportionate response to unspeakable acts.”

U.S. officials said the military intervention was a “one-off” intended to deter future chemical weapons attacks, and not an expansion of the U.S. role in the Syrian war.

The action is likely to be interpreted as a signal to Russia, as well as to countries such as North Korea, China and Iran where Trump has faced foreign policy tests early in his presidency, that he is willing to use force.

Assad’s office said Damascus would respond by striking its enemies harder.

The Syrian government and Moscow denied Syrian forces were behind the gas attack but Western countries dismissed their explanation that chemicals leaked from a rebel weapons depot after an air strike.

The Syrian army said the U.S. attack killed six people and called it “blatant aggression” which made the United States a partner of “terrorist groups” including Islamic State. There was no independent confirmation of civilian casualties.

U.S. lawmakers from both parties on Friday backed Trump’s action but demanded he spell out a broader strategy for dealing with the conflict and consult with Congress on any further action.

A Russian frigate carrying cruise missiles sailed through the Bosphorus Strait into the Mediterranean Sea, although there was no indication it was in response to the U.S. action.

Russia expects U.S. Secretary of State Rex Tillerson to explain Washington’s stance in light of the missile strikes

when he visits Moscow in the coming week, Interfax news agency cited a Russian Foreign Ministry spokeswoman as saying.

Washington has long backed rebels fighting Assad in a multi-sided civil war that has killed more than 400,000 people and driven half of Syrians from their homes since 2011.

The United States has conducted air strikes against Islamic State militants who control territory in eastern and northern Syria, and a small number of U.S. troops are on the ground assisting anti-Islamic State militias.

Russia joined the war on Assad’s behalf in 2015, turning the momentum of the conflict in his favor. Although they support opposing sides in the war between Assad and rebels, Washington and Moscow say they share a single main enemy, Islamic State.

Tuesday’s attack was the first time since 2013 that Syria was accused of using sarin, a banned nerve agent it was meant to have given up under a Russian-brokered, U.N.-enforced deal that persuaded Obama to call off air strikes four years ago.

Video depicted limp bodies and children choking while rescuers tried to wash off the poison gas. Russian state television blamed rebels and did not show footage of victims.

The U.S. strikes cheered Assad’s enemies, after months when Western powers appeared to grow increasingly resigned to his staying in power. But opposition figures said an isolated assault was far from the decisive intervention they seek.

(Additional reporting by Phil Stewart, Idrees Ali, Yara Bayoumy, Jonathan Landay, John Walcott, Lesley Wroughton, Patricia Zengerle, Roberta Rampton, David Brunnstrom and Matt Spetalnick in Washington, Megan Davies in New York and Jack Stubbs in Moscow; Writing by Peter Graff and Alistair Bell; Editing by Giles Elgood and James Dalgleish)