U.S. stocks ended down sharply Monday, with the S&P 500 and Nasdaq closing below a key technical indicator for the first time since April, as investors braced for quarterly results from retailers and chip giant Nvidia and also awaited a long-delayed U.S. jobs report this week.

Losses accelerated in afternoon trading as all three main indexes traded below their 50-day moving averages. This closely followed moving average is seen as a proxy for the intermediate-term trend.

Results this week from major retailers Walmart, Home Depot and Target will round out the quarterly earnings season.

Shares of Home Depot, due to report on Tuesday before the bell, ended lower.

Investors eagerly awaited the September jobs report, which is due to be released on Thursday after the long U.S. government shutdown ended last week.

Investors are waiting for two big things: "a look at the consumer ... and Nvidia's earnings," said Adam Sarhan, chief executive of 50 Park Investments in New York, noting that "you have a consumer that is potentially getting weaker, not stronger."

Also, he said, "we have got the market consolidating a very big rally from the April low."

Nvidia, the world's largest company by market value, which is at the heart of Wall Street's artificial intelligence trade, is due to report after the bell on Wednesday. Its shares fell on Monday and were among the biggest drags on the Nasdaq and S&P 500.

Stocks have been pressured this month by concerns that AI exuberance has driven up valuations to expensive levels.

According to preliminary data, the S&P 500 lost 61.44 points, or 0.90%, to end at 6,672.67 points, while the Nasdaq Composite lost 189.01 points, or 0.82%, to 22,710.70. The Dow Jones Industrial Average fell 554.34 points, or 1.18%, to 46,592.91.

Among the day's gainers, Google parent Alphabet rose to a record high after Berkshire Hathaway revealed a stake of $4.3 billion in the company.

Berkshire also further reduced its stake in Apple, whose shares ended lower on Monday.

Among other declining shares, Dell Technologies dropped after Morgan Stanley downgraded its rating on the AI server maker to "underweight" from "overweight."

Investors also digested views on the outlook for stocks next year. Brokerage Morgan Stanley expects U.S. stocks to outperform peers next year and prefers global equities over credit and government bonds.