Russian and Iranian forces last night warned Donald Trump that they would retaliate with military action against the United States if he launched more airstrikes on Syria.

The military chiefs said in a joint statement with militant group Hezbollah, “From now on we will respond with force to any breach of red lines and America knows our ability to respond well.”

The Russian Embassy in London suggested, on Sunday night, that there could be ‘real war’ if Moscow is presented with an ultimatum over Syria.

But UK Foreign Secretary Boris Johnson will lead a push on Monday for Russia to face tough new sanctions unless it withdraws its support for Assad.

Russian President Vladimir Putin met with President of the Islamic Republic of Iran Hassan Rouhani in Moscow on March 28

At a G7 meeting in Italy, Johnson will call for Moscow to be threatened with isolation from the international community and a raft of economic punishments.

The Kremlin mocked Britain for having ‘no real influence on the course of international affairs’ after M.  Johnson cancelled a planned trip to Moscow;

UK’s Defence Secretary Sir Michael Fallon said Russia was responsible for ‘every civilian death’ in Assad’s chemical weapons attack on his own people;

America warned Moscow it faces a ‘relationship of competition and potential conflict’ unless it stops supporting Assad’s ‘murderous regime’;

The White House told North Korea it should take US missile strikes against Syria as a warning that America is prepared to take military action against countries which break international agreements.

Despite the looming threat of war following the decision to launch airstrikes, Trump made his way on to his golf course in West Palm Beach, Florida on Sunday – marking his 16th visit to one of his own courses since he became president.

During the election campaign, Trump said that as president he would probably never see his own golf courses again because he’d be too busy working.

He also repeatedly attacked Barack Obama’s golf trips and vacations for at least five years during the previous administration and begged the former president not to attack Syria back in 2013.

The fallout comes after President Trump ordered airstrikes (pictured) on a Syrian airbase in the first direct attack by the US against Assad

But in the early hours of Friday morning, President Trump himself ordered airstrikes on a Syrian airbase in the first direct attack by the US against Assad.

The onslaught of 59 cruise missiles followed a suspected chemical attack on the rebel-held town of Khan Sheikhun in northern Syria which killed 87 civilians, including many children.

A joint command centre of Russia, Iran and Islamist militant group Hezbollah warned America they would not allow further attacks on the Syrian regime.

In a statement they said: ‘What America waged in an aggression on Syria is a crossing of red lines. From now on we will respond with force to any aggressor or any breach of red lines from whoever it is and America knows our ability to respond well.’

The phrasing appeared to be a mocking reference to Barack Obama’s warning in 2012 that Assad should not cross a ‘red line’ by using chemical weapons.

In a further sign of increasing tensions, the Russian Embassy in London responded with anger to claims the G7 – Canada, France, Germany, Italy, Japan, Britain and America – could today agree to slap Putin with the threat of sanctions unless he pulls his troops out of Syria and ends his support for Assad.

In a series of provocative tweets on its official account, the embassy suggested that if Russia were given an ultimatum, the outcome would be either, ‘war of clowns, war of muses, a conventional war or a mix of the above’.

The Russian Embassy in London responded with anger to claims the G7 could agree to slap Putin with the threat of sanctions. It added: ‘If G7 ultimatum to Russia brings us to real war, what is your trust in @realDonaldTrump as a wartime leader & @BorisJohnson as his lieutenant?’ Iran’s supreme leader, Ayatollah Ali Khamenei, last night said the US had made a ‘strategic mistake’ by attacking Syria.

He made clear he was not intimidated by claims the airstrike was a warning that America was willing to target other countries. Tehran has been a key backer of Assad in Syria’s six-year civil war.

‘The Islamic Republic of Iran will not leave the field in the face of threats. Former American officials created Daesh [Islamic State] and the current leaders are reinforcing it,’ Khamenei said.

Trump administration officials yesterday blamed Russian inaction for enabling the deadly poison gas attack against Syrian civilians last week. US Secretary of State Rex Tillerson said Syria was able to execute the attack, which killed scores of people, because Moscow had failed to carry out a 2013 agreement to secure and destroy chemical weapons in the country.

White House national security adviser HR McMaster said Syria’s ‘sponsors’, Russia and Iran, were enabling Assad’s ‘campaign of mass murder against his own civilians’.

He said the US would take further action in Syria if necessary. ‘We’re prepared to do more. The president will make whatever decision he thinks is in the best interests of the American people,’ he told Fox News.

Mr. McMaster said Moscow was supporting ‘a murderous regime’ and its actions would dictate the future of US-Russian relations.