Key events this week include the October US jobs report, the expected announcement by President Donald Trump of the next head of the Fed, and earnings from Apple and other large companies.

Analysts attributed the weakness Monday primarily to buyers' fatigue after a slew of stock market records over the last month.

Investors also were cautious after the first indictments connected to the investigation into Russia's connections to Trump's presidential campaign, although the cases do not directly connect to Trump himself.

The probe is seen as a potential threat to tax cuts that have helped propel the market higher.

The Dow Jones industrial Average fell 0.4 percent to close the session at 23,348.74.

The broad-based S&P 500 sank 0.3 percent to 2,572.83, while the tech-rich Nasdaq Composite Index declined less than 0.1 percent to 6,698.96.

The Nasdaq and S&P 500 finished at all-time highs on Friday.

Merck weighed on the Dow, slumping 6.1 percent following downgrades in response to the drugmaker's disappointing earnings Friday and after it pulled a European application for its cancer drug Keytruda.

Sprint sank 9.3 percent and T-Mobile US shed 5.4 percent following a Japanese media report that merger talks between the third- and fourth-largest wireless operators had been called off.

Apple, which reports earnings on Thursday, jumped 2.3 percent, gaining for a second straight session on bullish commentary from the tech company about its next iPhone.

Mattel surged 11.3 percent, bouncing after a big drop Friday on weak earnings, after BMO Capital Markets said the toymaker could be a takeover target.

In merger news, homebuilder CalAtlantic Group shot up 21.3 percent on news it agreed to be acquired by Lennar in a transaction valued at about $9.3 billion. Lennar dropped 4.0 percent.