Chairman Jerome Powell believes the Federal Reserve’s balance sheet will be significantly reduced from where its currently at, as he stated Thursday, indicating that an increase of monetary tightening is to follow. Although Powell didn’t specify just how much smaller the central bank’s portfolio of bonds would become, the comment seems to make the stock market slow during afternoon trading.

“It will be substantially smaller than it is now,” the chairman said during a discussion at the Economic Club of Washington. “It will be smaller than it is now, but nowhere near where it was before.”

CNBC reports that the Fed had been holding nearly $4.5 trillion worth of mostly Treasurys and mortgage-backed securities, which were accumulated during three rounds of monetary stimulus during and after the financial crisis.

Back in October 2016, the Fed enabled a fixed cap of proceeds derived from those bonds to run off each month, with the current level reaching a ceiling of $50 billion. Since the operation began, the Treasury and MBS holdings have contracted by about $400 billion. The balance sheet overall is currently below $4 trillion.

Wall Street began raising some concerns on whether the Fed should cut the balance sheet during the same time it raises its benchmark interest rate. The policymaking Federal Open Market Committee approved four rate increases in 2018,  further indicating two more are to follow this year.

Fed officials believe the run-off will happen with no disruption, while former Chair Janet Yellen compared it to “watching paint dry.” Powell also jumped to defend the operation during his chat with David Rubenstein, co-founder of the Carlyle Group. “We wanted to have the balance sheet return to a more normal level, which is a level no larger than it needs to be for us to conduct monetary policy,” he said.