Richard Drew, Associated Press
Specialist Fabian Caceres works at his post on the floor of the New York Stock Exchange Thursday, March 28, 2013.

NEW YORK — The stock market edged lower in early trading Monday as investors weighed the potential impact of a budget fight in Washington.

A rally in stocks last week that followed the Federal Reserve's decision to maintain its economic stimulus was erased by Friday, when the U.S. House of Representatives voted to defund President Barack Obama's health care law. That gesture reminded investors that the Republican-led House and the Democratic-controlled Senate are poised for a showdown over federal spending.

The Dow Jones industrial average fell 21 points, or 0.1 percent, to 15,426 as of 10 a.m. Eastern Daylight Time. The Standard & Poor's 500 index dropped six points, or 0.4 percent, to 1,703. The Nasdaq composite fell 5.2, or 0.1 percent, to 3,769.

Apple shares rose the most in the S&P 500 after the company said that shoppers had snapped up 9 million of its newest iPhones following the rollout of the devices on Friday. Apple surged $20.57, or 4.4 percent, to $488.

Blackberry, the Canadian smartphone maker that has seen the popularity of its products wane since the introduction of the iPhone, fell in early trading.

That extended a plunge in the company's stock on Friday, after Blackberry announced that it planned to cut 4,500 jobs and slash its spending as it shifts its focus back to business customers. On Monday, its stock dropped 46 cents, or 5.2 percent, to $8.23.

Goldman Sachs, Nike and Visa began trading on the 30-member Dow on Monday, replacing Alcoa, Bank of America and Hewlett-Packard.

In government bond trading, the yield on the 10-year Treasury note fell to 2.71 from 2.74 percent.

In commodities trading, the price of oil fell 80 cents, or 0.8 percent, to $103.90 a barrel. The price of gold fell $9.30, or 0.7 percent, to $1,322.80 an ounce.

The dollar rose against the euro and fell against the Japanese yen.