Phillips was outstanding for England as he started every game at Euro 2020, helping them to an eventual final defeat to Italy on penalties.
His club captain Cooper believes that Phillips is one of the very best midfielders on the planet at present.
"He announced himself in that first game against Croatia (at Euro 2020) and I've told him that his life has changed forever now," Cooper told Sky Sports News.
"He knows that though, he's not a stupid lad and lives his life the right way anyway.
"I've seen his journey from a young lad to where he is now and it's been a pleasure to see - and he belongs there.
"He works so hard here (at Leeds), all the boys and the people of Leeds think the world of him and he deserves everything that comes his ways.
"I've seen how hard he works every single day, I see how much he takes on and turns it into his game.
"For me, he is one of the best midfielders in the world right now."
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