Donald Trump used "Game of Thrones" to warn he was about to impose sanctions on Iran -- and while his supporters might've been amused ... HBO definitely is not.
A rep for the cable network tells TMZ ... "We were not aware of this messaging and would prefer our trademark not be misappropriated for political purposes."
In case you missed it, President Trump tweeted out a meme of himself with a 'GoT'-esque background and font that read ... "Sanctions are Coming."
It's an obvious nod to the hit series' oft-repeated line, "Winter is Coming" ... and it looks like he was trying to portray himself as Jon Snow (or maybe the Mad King?).
Either way, it's clear HBO is not down for the shout-out ... or the use of its font and background. Unclear if they plan on taking any further steps -- like a cease and desist letter or a lawsuit -- to keep Trump out of Westeros ... but this definitely sounds like a warning shot.