Donald Trump’s decision to launch a cruise missile attack on Syria proved he is not in league with Russia and will not be “pushed around” by Vladimir Putin, the US President’s son has told The Daily Telegraph.

Eric Trump said his father was not intimidated by President Putin’s talk of war, and there would be “no-one harder” than President Trump if they “cross us”.

He also confirmed that President Trump’s decision to bomb a Syrian airbase to punish President Bashar al-Assad for a nerve gas attack last week was influenced by the reaction of his sister Ivanka, who said she was “heartbroken and outraged” by the atrocity.

It came as Boris Johnson, the Foreign Secretary, said Russia would face fresh sanctions if it did not pull its armed forces out of Syria and end its support for Assad.

As foreign ministers of the G7 group of nations met to agree the best way to put pressure on Mr Putin, Mr Johnson said the US missile strike had “changed the game” and Russia now “needs a way out” because association with Assad’s “toxic regime is...poisoning the reputation of Russia”.