WASHINGTON — U.S. consumer confidence in September rose to the highest level in nine years, a hopeful sign that economic growth will accelerate in coming months.

The Conference Board said Tuesday that its consumer confidence index rose to 104.1, up from 101.8 in August, the strongest reading since August 2007.

Private economists had been forecasting the index would drop in September after a strong August. Many analysts expected that recent volatility in the stock market and some subpar economic readings on auto sales and manufacturing might lead consumers to feel less confident.

They also thought that increased uncertainty around the presidential campaign might weigh on consumers.

“It appears that steady job gains, low volatility in equity markets and subdued gasoline price pressures are helping consumers’ outlooks,” analysts at Contingent Macro Research said in a note to clients.