There is no way out other than Financial Repression. Treasury cannot cap the long rate on its own for a long time. Sustained control over long-term rates would eventually require cooperation from the Federal Reserve. The Federal Reserve can print money to buy long-term bonds, pushing down the yield, and that is quantitative easing (QE). A even more radical version was used in 1942–1951, when the Fed just capped long term Treasuries yield at 2.5%.(BloFin Research)