US stocks finished down Monday (6 March), off session lows, as geopolitical concerns rose and the realisation of a interest rate hike became clearer. Markets took a negative turn following reports that North Korea tested four ballistic missiles off of its east coast early in the day.

The Dow Jones Industrial Average, dropped 51.37 points, or 0.2%, to settle at 20,954.34. MarketWatch noted it was the first time the blue-chips gauge closed below 21,000 since clearing the milestone on Wednesday (1 March). Declines were let by shares of Travelers Cos and JP Morgan Chase & Co.

The S&P 500 finished down 7.81 points, or 0.3%, at 2,375.31. Ten of the index's 11 primary sectors closed in the red, with financials and materials leading decliners. The financials sector, which had been the biggest post election gainer, dropped 0.6% and materials fell 0.7%. According to MarketWatch, the energy sector was the only sector to close in the green, rising 0.3%.

Meanwhile, the Nasdaq Composite declined 21.58 points, or 0.4%, to finish at 5,849.17.

CME Group's FedWatch tool noted that market expectations for an interest rate hike were 86.4% on Monday, up from 30% this time last week. The Federal Reserve's monetary policy committee is scheduled to meet between 14 and 15 March.

"The March rate hike doesn't matter. What matters is how many times they raise," Jeremy Klein, chief market strategist at FBN Securities, told CNBC. "If they stay at three times [for this year], then the market will be fine." CNBC noted that the only possibly obstacle for the Fed to raise the rates in March is the February jobs report, due to be released on Friday (10 March).

Adding to investors' concerns is the proposed replacement to the Affordable Care Act (ACA) that congressional Republicans are expected to unveil sometime this week. "The market is waiting to see the specifics of that, its clarity, and how it's going to be implemented," Quincy Krosby, market strategist at Prudential Financial, told MarketWatch.

Investors are also monitoring the geopolitical ramifications of North Korea firing ballistic missiles on Monday. Three of the four missiles landed in Japan's exclusive economic zone, Japanese Prime Minister Shinzo Abe confirmed.

The US Dollar Index rose 0.1%, while gold settled down less than 0.1% at $1,225.50 (£1,001.39) an ounce. Oil prices also settled down 0.2% at $53.20 (£43.47) after Friday's (3 March) data from Baker Hughes Inc revealed another rise in the US rig count, MarketWatch reported.