US stocks opened lower on Monday as fading expectations of a breakthrough between the United States and Iran, elevated crude oil prices and renewed concerns over inflation weighed on market sentiment.

The Nasdaq 100 Index fell 0.8 percent by 9:55 a.m. in New York, putting the technology heavy index on course to erase gains recorded over the previous two sessions. The S&P 500 Index declined 0.5 percent. ARM Holdings, Sandisk and Datadog were among the notable decliners.

Investor attention remained focused on developments between the US and Iran, with the two sides appearing far apart on a potential ceasefire agreement and the reopening of the Strait of Hormuz. Iran has maintained its position on a proposal that was rejected by US President Donald Trump, adding to uncertainty over the outlook for regional tensions and global energy supplies.

The lack of progress has contributed to renewed pressure on crude oil prices, with Brent crude trading around $107 a barrel despite the restart of exports through a key Saudi Arabian oil pipeline. Higher energy prices are also raising concerns about their potential impact on inflation and monetary policy.

The Treasury market also came under renewed pressure, with selling in US government bonds pushing yields higher. Investors are increasingly focused on whether stronger economic data could reinforce expectations that US interest rates may need to remain elevated for longer.

A series of US economic indicators due this week could provide further insight into the strength of the economy. Consumer confidence data for September and August job openings data from the JOLTS report are scheduled for release on Tuesday. Stronger economic readings could reinforce arguments from some Federal Reserve officials that interest rates should remain higher.

The artificial intelligence sector is also expected to remain in focus, with Micron Technology scheduled to report quarterly results on Wednesday after the US market closes. Investors are expected to closely assess revenue growth, margins, demand expectations and earnings, particularly as rising memory costs create pressure on profitability across the AI supply chain.

Among individual stocks, Nvidia gained after announcing a record $150 billion increase in its share buyback authorization. MongoDB, meanwhile, fell sharply after Meta Platforms appointed MongoDB’s president and chief executive officer to lead a new enterprise focused AI platform.

The combination of geopolitical uncertainty, elevated oil prices, higher Treasury yields and upcoming economic and corporate earnings data is keeping investors focused on potential weak links across US equity markets.