The selloff in US Treasuries could resume unless the Federal Reserve provides investors with a clearer plan for bringing inflation back to its 2% target, according to Bank of America rates strategist Mark Cabana.

Cabana described last week’s sharp rise in long dated Treasury yields as a “textbook inflation credibility shock” triggered by Fed Chair Kevin Warsh’s failure to explain how the central bank intends to contain persistent price pressures.

“It’s wonderful you’re resolute in your determination to have 2% inflation, but unless you tell us how you’re going to do it, we will not believe you,” Cabana said during a Bloomberg TV interview. “And you can’t fool the bond. It will see through it.”

The warning follows the Fed’s decision on July 29 to leave its benchmark interest rate unchanged at between 3.5% and 3.75%. Three officials dissented in favor of a rate increase as concerns grew that inflation could remain above target.

Warsh reiterated the Fed’s commitment to price stability but offered limited guidance on the path of monetary policy. His approach reflects a broader move away from forward guidance, under which central bank officials signal the likely direction of future interest rates.

The lack of detail unsettled bond investors and pushed the 30 year Treasury yield as high as 5.28% on Friday, its highest level in almost two decades. The yield eased to around 5.22% on Monday morning.

The term premium on the 30 year Treasury, which represents the additional compensation investors demand for holding longer dated debt, climbed to 1.51% last week, according to Bloomberg Economics modeling. That marked its highest level since December 2013.

Bank of America economists said it is now “imperative” for the Fed to pass its September credibility test by raising rates and regaining control of the policy narrative.

Cabana said Warsh’s rejection of traditional forward guidance was not necessarily the central problem. Instead, markets are concerned that the Fed has not presented an alternative framework showing how it will respond if inflation remains elevated.

“We are looking for a plan, and we don’t see one right now,” Cabana said. “And that’s what the long end of the rate curve is telling you.”

Six members of the Fed’s rate setting committee are scheduled to speak this week, giving officials an opportunity to clarify the central bank’s inflation strategy. New York Fed President John Williams said Monday that the Fed is prepared to raise rates if inflation does not return toward 2%, although he expects some recent price pressures to ease.

Warsh is expected to offer a broader explanation of his policy framework at the Jackson Hole economic symposium. Investors will be watching for details on how the Fed plans to balance persistent inflation, elevated energy prices and pressure from the White House for lower borrowing costs.

Continued increases in long term Treasury yields could tighten financial conditions even without another Fed rate increase. Higher government bond yields raise borrowing costs and make lower risk assets more competitive with stocks and crypto assets, creating potential pressure on risk sensitive markets.