BlackRock’s Larry Fink said Monday that he is concerned that the overall stock market is being driven up by just a few technology names.

The S&P 500 has risen nearly 5 percent this year, but the lion’s share of that gain comes from a small number of technology stocks. Amazon, Netflix, Microsoft and Apple are responsible for 83 percent of the S&P 500’s return for 2018. Overall, tech shares are up more than 15 percent in 2018 and 30 percent over the past 12 months.

“If you strip out a handful of outperforming tech stocks, the lack of breadth in the equity markets is troubling,” Fink, CEO of the world’s largest asset manager, said in a conference call with analysts. “We are at a pivotal point. Clients are struggling to better understand increased risk and uncertainty.” He added that “market dynamics are shifting, causing those clients to pause as they think about the future.”

Investors have been on edge recently as a trade conflict between the world's two largest economies has escalated. Last week, the Trump administration unveiled a list of $200 billion in Chinese goods it will potentially target with 10 percent tariffs. The announcement came just days after both nations imposed tariffs on $34 billion of each other's goods.

Global investors have also dealt with political uncertainty as populist candidates have emerged victorious in elections in Europe and Latin America.

“Some of the strongest foundational components of international investing are being tested as trade frictions escalate to new levels,” Fink said. “Governments are changing heads in Italy and Mexico and further questions around other elections and policy decisions continue to challenge investors' confidence.”

Fink made his comments after BlackRock reported better-than-expected revenue and profit for the second quarter, though it also announced a slowdown in investment inflows amid the increasing uncertainty in the market.