Stocks are trading slightly lower after a historic streak of record highs

US stocks opened slightly lower on Monday as investors paused to assess Wall Street's recent record-setting run.

Investors will be closely watching President Donald Trump's address to a joint session of Congress on Tuesday evening for clues on his proposed tax reform and his plans to overhaul the Affordable Healthcare Act.

Trump's promise a few weeks ago of a "phenomenal" tax announcement helped rekindle a post-election rally, driving the main U.S. markets to record highs.

But since then, markets have traded range-bound amid caution due to sparse details on Trump's agenda. Utilities and telecom services stocks - traditionally defensive plays of the S&P 500 index - outperformed the other sectors last week.

The Dow Jones Industrial Average hit its 11th straight record close on Friday, despite just a 0.05 percent rise.

"The market activity suggests another mixed session today as investors await the key events of the week," Peter Cardillo, chief market economist at First Standard Financial wrote.

The Dow was down 30 points, or 0.15%, at 9:58 a.m. ET. The S&P 500 was down 2 points, or 0.1%, and the Nasdaq was down 5 points, also 0.1%.

Among stocks, electric carmaker Tesla slipped 3.1 percent to $249 in premarket trading after Goldman Sachs downgraded the company's stock to "sell" from "neutral" and lowered its price target.

Apple edged up 0.2 percent after Warren Buffett told CNBC that Berkshire Hathaway had bought 120 million shares of the iPhone maker this year.

La Jolla Pharmaceutical jumped 30 percent to $25.76 following the success of its lead experimental drug in a late-stage study.

Shutterstock dropped 11 percent to $46 after the stock image provider reported quarterly revenue that missed analysts' average estimate.