Stocks in weak open

NEW YORK (CNNMoney.com) -- U.S. stocks opened slightly weaker Monday as investors mulled last week's record-setting rally and braced for the start of the third-quarter earnings reporting period.

Shortly after the market's open, the Dow was down 9 points, at 14,057 and the S&P 500 was down 3 points, at 1,554.

Stocks soared on Friday after a strong employment report eased recession fears. The Dow Jones Industrial Average touched a record trading high and the broader S&P 500 index reached a record high close.

Warren Buffett's Berkshire Hathaway sold a block of listed shares in PetroChina for the fifth time in three months, dropping its stake in the company's share capital to 6.97 percent, according to a filing to the Hong Kong stock exchange Monday.

More labor strife could be brewing in the auto industry, as the United Auto Workers union gave 72-hour notice to Chrysler that it would end the contract extension under which its 49,000 members at the automaker have been working since Sept. 13. The notice could open the door for a strike at Chrysler, which in August was purchased from German automaker Daimler (Charts) by U.S. private equity firm Cerberus Capital Management.

Even if a deal is not reached in the next three days, the union might stay on the job on an hour-to-hour basis while talks continue. The union did that for more than a week at General Motors (Charts, Fortune 500) last month before it eventually waged a two-day strike there that was followed by a tentative labor deal. Ford Motor (Charts, Fortune 500) is also in talks with the union on a new labor deal, but the union has not given it a 72-hour notice of the end of its contract extension.

This week, investors will get a closer look at how corporate profits are faring amid the economic slowdown. Dow components Alcoa (Charts, Fortune 500) and General Electric (Charts, Fortune 500) kick off earnings season this week. Alcoa is due to report on Tuesday and GE is set for Friday.

There are relatively few companies set to report Monday and trading volumes could be light due to the Columbus Day holiday that will close Treasury markets and many banks and government offices. But U.S. stock markets will be open. Low trading volumes typically leads to greater volatility in the major indexes.

The largest company set to report results Monday will be YUM Brands (Charts, Fortune 500), which is due to report earnings after the market close. Analysts are forecasting improved earnings at the the fast food retailer, which owns Taco Bell and KFC.

In other corporate news, German software giant SAP (Charts) agreed Sunday to acquire French software maker Business Objects (Charts) in a tender offer valued at more than $6.8 billion.

GlaxoSmithKline (Charts) Monday said it picked Andrew Witty, the president of its European unit, to succeed CEO Jean-Pierre Garnier starting in May. Shares of the British drugmaker slipped 0.8 percent in London trading in morning trading there Monday.

Markets in Asia took cues from Wall Street's rally, with benchmark indexes in South Korea and Shanghai soaring to record highs. The Japanese market was closed for a holiday. In Europe, stocks struggled in morning trading.

Another batch of economic readings will also help determine whether the upbeat sentiment in the stock market holds. Among the most closely watched economic reports will be the minutes from the Federal Reserve's Sept. 18 meeting, due on Tuesday. At that meeting the central bank agreed to cut its benchmark interest rate for the first time in four years.

Oil prices slipped lower Monday as the price dropped below the $81 a barrel mark. Light, sweet crude for November delivery fell 44 cents to $80.78 in trading in Asia.