WASHINGTON — The Federal Reserve said Wednesday that it will keep buying government bonds until the economy makes “substantial” progress — a step intended to reassure financial markets and keep long-term borrowing rates low indefinitely.

The Fed also reiterated after its latest policy meeting that it expects to keep its short-term benchmark interest rate near zero through at least 2023. The Fed has kept its key rate there since March, when it took a range of extraordinary steps to fight the pandemic recession by keeping credit flowing.

In a series of economic projections Wednesday, though, Fed officials painted a brighter picture for next year, compared with its previous projections in September. The improvement likely reflects the expected impact of new coronavirus vaccines. The policymakers now foresee the economy contracting 2.4% this year, less than the 3.7% decline it envisioned in September.

By the end of 2021, the Fed expects the unemployment rate to fall to 5% from the current 6.7% — lower than the 5.5% rate it had forecast in September.

The Fed’s latest policy statement coincides with an economy that is stumbling and might even shrink over the winter as the raging pandemic forces new business restrictions and keeps many consumers at home. Weighing the bleak short-term outlook and the brighter long-term picture has complicated the Fed’s policymaking as it assesses how much more stimulus to pursue.