U.S. President Donald Trump's move to reimpose a naval blockade on Iran weighed on U.S. stocks on July 13.NEW YORK (Reuters) -- Tech shares weighed on U.S. stocks on Monday after President Donald Trump announced that he would reinstate a blockade on Iranian ports in the latest escalation of U.S.-Iran hostilities that sent oil prices jumping and dampened risk appetite.Investors stared down what promised to be an eventful week packed with earnings, economic data and congressional testimony from U.S. Federal Reserve Chair Kevin Warsh.Among the three major U.S. stock indexes, the tech-laden Nasdaq led the losses, followed by the S&P 500. The Dow's drop was cushioned by rising energy stocks, which were boosted by spiking crude prices due to restricted traffic through the Strait of Hormuz."The market's first impulse is to look through [geopolitics] and wait and see," said Ross Mayfield, investment strategy analyst at Baird in Louisville, Kentucky. "It seems like a lot of the weakness is concentrated in the memory space, which has been ongoing for the last six weeks or so, with incredibly volatile moves, a pause in the parabolic upswing of the memory and semi names."Amid the ongoing AI fervor of recent months, chip stocks have tended to take the lead through rally and sell-off. The Philadelphia SE Semiconductor index was a clear underperformer, with constituents Sandisk, Marvell Technology and Western Digital down between 6.5% and 12.3%.U.S.-listed shares of South Korean chipmaker SK Hynix sank 6.1% after rising more than 12% on Friday in their Nasdaq debut.The U.S. and Iran exchanged heavy airstrikes over the weekend, marking a sharp escalation in the scale and reach of attacks and prompted Trump to revive the U.S. blockade on Iranian ports, raising concerns about the path forward for peace negotiations. Crude prices surged 8.5%, fueling worries that strained supply and upward energy price pressures could broaden into long-term, systemic inflation.Warsh is due to sit for his first semiannual testimony before Congress this week, during which the new head of the central bank will be questioned regarding the inflationary effects of the U.S.-Iran war and the Fed's likely course of action.Markets are pricing in at least one 25 basis point rate hike by year-end, according to LSEG data.To that end, the Labor Department is expected to release its consumer and producer price indexes this week, which will give markets and the Fed a glimpse at the extent to which the on-again, off-again U.S.-Iran war affected price growth in June.The Commerce Department's June retail sales data will provide insight into how well the consumer, who accounts for about 70% of the U.S. economy, is weathering the price squeeze at the gasoline pump and elsewhere.The Dow Jones Industrial Average fell 136.25 points, or 0.26%, to 52,500.76, the S&P 500 lost 51.60 points, or 0.68%, to 7,523.79 and the Nasdaq composite lost 371.75 points, or 1.41%, to 25,911.51.Among the 11 major sectors of the S&P 500, tech shares suffered the biggest percentage loss, while energy led the gainers.Major financial firms Bank of America, Citigroup, Goldman Sachs, JPMorgan Chase and Wells Fargo were all slated to report quarterly results on Tuesday, marking the unofficial start of second-quarter earnings season."I wonder if the market is going to really start to revolt a little bit at the deluge of corporate issuance to fund this AI capex that has been called into question for a couple of years now," Mayfield added. "It'll be interesting to see down the road how the big banks talk about corporate bonds, fixed income, and what they have on their books or not."Analysts currently expect aggregate second-quarter S&P 500 earnings growth of 23.7% year on year, up from the 19.2% estimates as of April 1, according to LSEG.Declining issues outnumbered advancers by a 1.57-to-1 ratio on the NYSE. There were 126 new highs and 147 new lows on the NYSE.On the Nasdaq, 1,620 stocks rose and 3,060 fell as declining issues outnumbered advancers by a 1.89-to-1 ratio.