Treasury Secretary Janet Yellen cautioned Tuesday that inflationary pressures hitting the U.S. economy could last for a while.

Coming less than a week after Federal Reserve Chairman Jerome Powell called inflation “frustrating,” Yellen told CNBC that the various issues that have colluded to push up prices likely will pass though she’s not sure how long that will take.

“Supply bottlenecks have developed that have caused inflation,” she said during a live “Squawk Box” interview. “I believe that they’re transitory, but that doesn’t mean they’ll go away over the next several months.”

Fed officials often use the word “transitory” to describe the current run that has inflation running at a 3.6% year-over-year rate, a 30-year high, according to their preferred gauge. Other measures of inflation, such as the consumer price index, are registering considerably higher, and some economists believe the Fed is understating the durability of inflation.

The Fed targets inflation to run at 2% but said in its most recent consensus estimate from the Federal Open Market Committee that the level likely will be around 3.7% in 2021 before decreasing in following years. St. Louis Fed President James Bullard said Monday that he thinks inflation could run as high as 2.8% in 2022, compared to the broader Fed outlook for 2.3%,

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