NEW YORK — A quiet day on Wall Street turned into the worst sell-off in three months after a Federal Reserve official said he doubted the bank’s effort to boost economic growth would work.

Charles Plosser, president of the Fed’s Philadelphia branch, told an audience Tuesday that the Fed’s effort to support the economy would likely fall short of its goals.

The speech probably startled some investors who had faith in the Fed’s latest plan, said Jack Ablin, chief investment officer Harris Private Bank. The plan includes buying $40 billion in mortgage bonds each month until the economy improves.

“So many investors have bought into the illusion,” he said. “And it was like Plosser pulled up the curtain on the Wizard of Oz.”

The Standard & Poor’s 500 index lost 15.30 points, its fourth straight decline, to close at 1,441.59. The 1.05 percent drop was the worst for the S&P since June 25.

The Dow Jones industrial average lost 101.37 points to close at 13,457.55. Caterpillar tugged the Dow down, losing 4 percent. The world’s largest maker of bulldozers and other heavy equipment said late Monday that slower economic growth around the world dampened its earnings forecast. Its stock sank $3.86 to $87.01.