Hedge-fund veteran Stanley Druckenmiller delivered a blunt rebuke to his longtime protégé, Treasury Secretary Scott Bessent, over his plans to intervene in the government bond market to bring down interest rates.

Spending $4 billion or more to buy back long-dated Treasury bonds is a "mistake" that won't address the fundamental reasons behind the rise in the U.S. government's borrowing costs, Druckenmiller wrote in a scathing op-ed in The Wall Street Journal.

Those reasons include a surging budget deficit and national debt-which surpassed $40 trillion last week-as well as persistent inflation, according to Druckenmiller. Attempting to push down the 30-year Treasury yield will only stave off America's fiscal reckoning, which will ultimately require reforms to popular social benefits, he warned.

"The long-term Treasury yield is the most important price in the world. It is also the only fiscal disciplinarian the U.S. has left," Druckenmiller wrote.

If the message wasn't unique-some bond investors have made similar criticisms-what's drawing attention is the messenger. The 73-year-old worked with Bessent at legendary hedge fund Soros Fund Management and has long been viewed as his mentor.

Druckenmiller is also close to Fed Chairman Kevin Warsh, who-much like Bessent-is facing pressure from President Trump to bring down interest rates ahead of November's midterm elections.

Druckenmiller, who was Warsh's boss for over a decade, has long railed against excessive government borrowing and reveres former Fed Chairman Paul Volcker, who tamed inflation by raising interest rates high enough to cause a painful recession and regain the Fed's credibility.