U.S. equities traded higher on Tuesday as investors remained unfazed by geopolitical tensions, while the Dow Jones industrial average kept marching toward 20,000.

The blue-chips index was 0.59 percent away from reaching the milestone mark, entering Tuesday trading. In midmorning trade ET, it rose about 90 points, hitting a new intraday high, with Goldman Sachs contributing the most gains. The S&P 500 rose 0.33 percent, with financials and telecommunications leading advancers. The Nasdaq composite advanced 0.4 percent, also reaching a new all-time high.

On Monday, the Russian ambassador to Turkey died after being shot by a gunman at an art gallery in the Turkish capital. Meanwhile, in Berlin, a truck ploughed into a crowded Christmas market, killing 12 and injuring 48.

European equities traded mostly higher Tuesday, as the pan-European Stoxx 600 index rose around 0.4 percent. "If the pattern is something we've seen before, the market is going to look right through it," said Quincy Krosby, market strategist at Prudential Financial.

U.S. stock futures drifted higher before the bell, with trading volume beginning to drop ahead of the Christmas holiday. "As we go deeper into the week, the volume will continue to fall off," said Krosby. "That's important because any strong headline can skew the market in one direction or another."

The U.S. composite volume totaled 6.17 billion shares, the lowest since Nov. 25, when only 3 billion shares were traded.

Specialist trader Mario Picone wears a "DOW Almost 20,000" cap as he works at his post on the floor of the New York Stock Exchange (NYSE) in New York City, U.S., December 15, 2016.

There are no major economic data due Tuesday, but investors had several earnings reports to chew on, with the likes of Darden RestaurantsGeneral Mills and BlackBerry all reporting before the bell. FedEx and Nike are also scheduled to report after the close.

"Along with [Oracle], which delivered their earnings last week, and [Accenture], which will do the same tomorrow morning, these releases will offer a good preview for the upcoming reporting season," Jeremy Klein, chief market strategist at FBN Securities, said in a note, referring to Nike and FedEx's results.

Analysts polled by Reuters expect Dow-component Nike to report earnings per share of 43 cents on sales of 8.1 billion. FedEx is expected to post profits of $2.90 per share on revenue of $14.92 billion.

U.S. Treasurys resumed their sell-off after a slight uptick following the events in Ankara and Berlin, with the benchmark 10-year note yield rising to 2.5856 percent and the short-term two-year note yielding 1.236 percent.

The dollar rose 0.38 percent against a basket of currencies, with the euro trading at $1.037 and the yen near 118.1.

In oil markets, U.S. crude rose 0.83 percent to $52.55 per barrel amid expectations for falling U.S. stockpiles.