The blowhard has a history of spewing retaliatory threats at Putin, then wimping out.
Less than a month ago, Trump welcomed Putin to a summit in Alaska, rolling out the red carpet, warmly embracing the architect of the war in Ukraine...
But far from progress towards a deal, the weeks since have brought only escalation. More record-breaking Russian drone and missile attacks on Ukraine, and now, for the first time, a flagrant incursion into NATO airspace...
For such assurances, if given, to have been so flagrantly cast aside will inevitably be seen in the Gulf as a sign of American weakness.
Despite Russian denials, there's a near universal consensus that this was a deliberate effort by Moscow to test Nato's resolve.
And since the United States remains the alliance's most powerful member, that means testing Donald Trump's resolve too.
Trump's apparent reluctance to respond... did not go unnoticed.
"A stunning silence from the White House greeted news that a Nato ally for the first time engaged and shot down Russian military assets," the Kyiv Post newspaper wrote.