President Donald Trump’s demand on Wednesday that the Federal Reserve slash its benchmark interest rate “to zero or even negative” is misguided, economists say, because rates that low would be a sign of weak economic conditions.

“Trump is confused. European rates are low because Europe is in trouble,” said Robert Brusca, chief economist at FAO Economics.

Carl Weinberg, chief economist at High Frequency Economics, noted that when a 10-year government note has negative interest rates, it is worth less than “a bag of dirt stored in your basement.”

Negative bond yields is a “red flag” that money has lost its value, he said. The risk is it may trigger “feckless spending”

Trump is the first U.S. president to say that he would want interest rates below zero.

Jeremy Siegel, finance professor at the Wharton School at the University of Pennsylvania, said he thinks the Fed’s benchmark federal funds rate should be lowered, but not to zero or even negative.

At the moment, the Fed’s benchmark rate is in a range between 2%-2.25%. Siegel said he’d like to see the fed funds rate down between 1%-1.5%.

That would put rates below the yield on the 10-year Treasury note TMUBMUSD10Y, 0.657% .

Fed watchers expect the U.S. central bank to be much more cautious and trim its policy rate by a quarter point to 1.75%-2% at its policy meeting next week. There is a lively debate among analysts about how low rates will ultimately go. Fed officials have stressed they are not anticipating a major easing.

Yields on U.S. 10-year notes have fallen from 3.45% last November to as low as 1.46% in late August.

Negative rates would mean that a recession was inevitable, Siegel said.

Diane Swonk, chief economist at Grant Thornton, agreed, saying on Twitter that a steep drop in the Fed’s benchmark rate would be a signal to the market that the economy was much weaker than it appears.

Interest rates are at zero on government debt in Japan and Europe because those regions are barely growing economically. In contrast, the U.S. has had economic growth above 2% this year, she said.

Trump also tweeted that the U.S. should “refinance” its nearly $17 trillion outstanding debt.

This is also a puzzle to economists because the U.S. Treasury debt is not callable, like a mortgage, that can be paid off early. The Treasury debt that pays a high interest rate has to run off in order to be refinanced at lower yields.

But it makes a lot of sense for the government to issue new long-term debt with interest rates so low, Siegel said.