US Federal Reserve Chairman Jerome Powell and his colleagues are loathe to follow Europe and Japan into negative interest rate territory — no matter what US President Donald Trump might want or how bad the US economy might get.

Not only could such a move be deemed illegal, it is also unclear how much of an economic gain it would yield given the likely disruption it could cause to banks and money market funds.

“I don’t see negative interest rates being a very useful part of our arsenal,” Fed Governor Lael Brainard said in a televised interview with Yahoo Finance in June.

Trump on Wednesday urged the Fed to “get our interest rates down to zero or less,” arguing in a tweet that the move would allow the US government to bring the cost of servicing its debt “way down.”

The tweet came a day before the European Central Bank (ECB) cut its deposit rate by 10 basis points to minus-0.5 percent, a penalty rate that pushes banks to lend excess cash.

The ECB also said it would restart its bond-buying stimulus program, which pumps newly created money into the financial system to lower borrowing costs and help the economy. It is to buy 20 billion euros (US$22 billion) per month in government and corporate bonds for as long as needed.

It also extended its promise to keep rates at record lows until inflation has “robustly” converged on its goal of just less than 2 percent.

With unemployment near a half-century low and the economy still expanding, the Fed is a long way from slashing rates to zero or below.

However, it is widely expected to cut rates by 0.25 percentage points next week to a range of 1.75 to 2 percent in response to muted inflation and slowing global growth.

The more pertinent question is whether the Fed would push rates into negative territory if the US economy tumbles into a recession.

Based on policymakers’ public and private comments, the answer is probably not.

Instead, they would look to other tools — such as large-scale bond purchases and forward interest-rate guidance — to try to provide the economy with a needed boost.

Negative rates are “way down the list of things that they would do,” Johns Hopkins University professor and former Fed economist Jonathan Wright said.

The gains are limited, while the political fallout — Trump to the contrary — could be large.

When the Fed in 2008 reduced rates to a range of zero to 0.25 percent and kept them there for seven years, it was frequently criticized by lawmakers for short-changing savers.

The Fed is in the midst of a wide-ranging strategic study of ways it could tackle what Powell has called the “key question” facing it: How could it best manage the ups and downs of the economy in a world of permanently lower interest rates?

However, negative rates do not seem to be high on the agenda. A listing of Fed research relevant to the review on the central bank’s Web site does not include a section on negative rates, JPMorgan Chase & Co chief US economist Michael Feroli said.

What is more, two of the academic papers presented at a Chicago Fed conference on the review — including one coauthored by Wright — cast doubt on how effective they can be.

Additional reporting by AP