NEW YORK — The stock market extended its slide to a fourth day as investors worried that a weak job market will trip up a recovery in the economy.

Stocks posted modest losses yesterday, a day after tumbling on fears about the health of banks and concerns that a six-month rally has left the stock market overheated.

A private sector report on unemployment gave investors new reason to fret about what is widely seen as the biggest problem facing the economy. The ADP National Employment Report found that employment fell by 298,000 in August following a revised loss of 360,000 jobs in July. The losses were the smallest since September 2008 but more than analysts had expected.