Investing.com - JPMorgan Chase (NYSE:JPM) is warning investors about tech stocks as the U.S. and China square off over trade.In a note to clients, the firm said that "the adverse trade impact could be material" and put tech stocks "under pressure."Trade tensions soared last week after the Trump administration said it would impose tariffs on some $60 billion of Chinese goods, a move that prompted Beijing to say it may retaliate with tariffs on more than 100 U.S. products. China has since said it is willing to hold talks to resolve the issues.JPMorgan advises investors to lock in profits after "years of outperformance", adding "tech valuations are no longer attractive."Tech stocks have surged during the nine-year bull run, outperforming the broader market. They were also the hardest hit in last week's Wall Street selloff, triggered by the U.S.-China trade row.