Mr. Powell could use his appearance to suggest that the central bank, which has been pledging to “act as appropriate” to sustain the expansion, now plans to follow that 1990s template — taking a break after October, and waiting to see whether economic data come in soft enough to merit further action.

“I think he’ll try to differentiate what the Fed has been doing from the next stage, which will be more data-dependent,” said Michelle Meyer, United States economist at Bank of America. “He’ll have to elaborate on what exactly that means — what is ‘act as appropriate,’ at this point?”

Relatively few investors are betting on a fourth 2019 rate cut, though market pricing suggests many see another reduction by next summer.

Hints at a coming pause could usher in criticism from Mr. Trump, who has spent more than a year pressuring the politically independent central bank to more aggressively cut borrowing costs.

The president, who appointed Mr. Powell as chair, said last week on Twitter that the Fed would be “derelict in its duties” if it failed to lower rates further. He compared the central bank unfavorably to Germany, where the European Central Bank has recently cut rates deeper into negative territory. While Mr. Trump often repeats that complaint, economists and central bankers point out that Europe’s economy is experiencing a more severe slowdown than the United States, necessitating a monetary policy response.

Fed officials have said repeatedly that they ignore politics and set monetary policy based on the economic outlook.

Whatever Mr. Powell and his colleagues signal about future monetary policy, it is likely to be vague enough to leave options open. The Fed’s final 2019 meeting is Dec. 10-11, giving officials a month and a half of economic data and geopolitical developments to parse before they have to make another decision.