US stocks continued on a downward turn on Tuesday (11 April), closing with narrow losses as investors remain cautious amid continued geopolitical tensions. Shares of United Continental plummeted earlier in the session, wiping out roughly $675m of the company's market capitalisation, before clawing back some gains.

The Dow Jones Industrial Average dropped 6.72 points, or 0.03%, to settle at 20,651.30. MarketWatch said the blue-chips gauge fell as much as 146 points at its intraday nadir. Apple, which was hit by a countersuit from chipmaker Qualcomm over a dispute on mobile technology licensing fees, contributed the most to losses.

According to CNBC, Dow transports also took a hit as shares of United Continental briefly slid more than 4% as outrage over a passenger being forcibly removed from an overbooked flight took effect. The airline's stock bounced back but still ended down 1.1%, wiping out $225m off the airline's market cap.

The S&P 500 index slid 3.38 points, or 0.1%, to end 2,353.78, with the technology and financials sectors leading losses. Meanwhile, the Nasdaq Composite fell 14.15 points, or 0.2%, to close at 5,866.77, with tech stocks declining for an eighth consecutive session.

Investors remained cautious as they monitor the latest geopolitical developments involving the US' stance on Syria at a G-7 meeting and rising tensions with North Korea. Pyongyang has warned it is open to war if US Navy ships move closer to the Korean Peninsula, MarketWatch noted.

"Investors do not see a war breaking out on the [Korean] Peninsula, but Donald Trump prides himself as being unpredictable and there are lingering worries that he may be irrational on trade with any country with a trade surplus," Bruce McCain, chief investment strategist at Key Private Bank, told MarketWatch.

A US official told Reuters on Saturday (8 April) that a US Navy strike group would be moving closer to the Korean Peninsula as a show of force. Trump took to Twitter on Tuesday to discuss the rising tensions with North Korea and the role China could play. "North Korea is looking for trouble. If China decides to help, that would be great. If not, we will solve the problem without them! USA," the president tweeted.

Investors are also concerned about the president's ability to implement measures to stimulate economic growth, according to MarketWatch. White House Press Secretary Sean Spicer said Monday (10 April) would not confirm when tax reform would pass, but said he would like to see it pass by August.

Gold futures for June delivery rose $20.30 to settle at $1,2724.20 an ounce, CNBC reported. Meanwhile, US Treasurys rallied to send yields near their lowest levels in months. The benchmark 10-year yield dropped 6 basis points to 2.3%.