Wall Street indexes fell on Monday as a fresh escalation between the U.S. and Iran in the Gulf pushed oil prices higher and unnerved investors, while chip stocks extended their recent slide.

President Donald Trump said the U.S. was reinstating its blockade of Iranian shipping in the Gulf and would keep the Strait of Hormuz open after the two sides exchanged further missile and drone attacks over the weekend.

The escalation undercuts an interim U.S.-Iran agreement signed last month that aimed to reopen the strait and end the war after 60 days of negotiations.

Crude futures rose about 5% after investors weighed the renewed threat to the shipping route.

The tech-heavy Nasdaq led declines, with semiconductor stocks among the hardest hit.

Memory-chip makers, which had rallied sharply this year, extended their recent pullback. Western Digital fell 6%, Micron Technology dropped 5% and Sandisk tumbled 10%, making them among the biggest decliners on the S&P 500.

“These memory shares have attracted a lot of investor interest in a short period of time since the beginning of the year. That kind of move is not normal, even though demand for their products is very strong,” said Robert Pavlik, senior portfolio manager at Dakota Wealth.

“Money is leaving this part of the market today, nervous investors are selling, and that selling creates even more downward pressure.”

Five of the 11 S&P 500 sectors were lower, with information technology down 1.4%, the weakest performer. The Philadelphia SE Semiconductor index fell 3.7%, leaving it more than 14% below its late-June record high.

U.S.-listed shares of South Korean chipmaker SK Hynix fell 9% after a blockbuster Nasdaq debut on Friday.

Earlier in the session, shares of Elon Musk’s rockets-to-AI company SpaceX touched their lowest level since going public last month. They were last down 4%.

At 11:59 a.m. ET, the Dow Jones Industrial Average fell 148.53 points, or 0.28%, to 52,488.48, the S&P 500 lost 37.18 points, or 0.49%, to 7,538.21 and the Nasdaq Composite lost 278.38 points, or 1.06%, to 26,003.23.

The pullback came ahead of a busy week of economic data and corporate earnings that could test the durability of the U.S. equity rally.

The S&P 500 is up more than 10% this year and less than 1% below its early-June record close. The benchmark posted a second straight weekly gain last week, despite volatility in semiconductor shares and renewed U.S.-Iran tensions that put inflation risks back in focus.

Major Wall Street banks will kick off the second-quarter earnings season this week.

S&P 500 earnings are expected to rise 23.7% in the second quarter from a year earlier, according to LSEG I/B/E/S.

Investors will also parse several key economic reports, starting off with Tuesday’s U.S. consumer price index, an inflation reading that could reset expectations for the path of interest rates.

On Tuesday, Fed Chair Kevin Warsh is expected to deliver his first monetary policy testimony before Congress.

Markets are pricing in at least one 25-basis-point rate hike by year-end, according to LSEG data.

Advancing issues outnumbered decliners by a 1.34-to-1 ratio on the NYSE and by a 1.75-to-1 ratio on the Nasdaq.

(Reporting by Ragini Mathur and Avinash P in Bengaluru; Editing by Maju Samuel)