April 28 (Reuters) - Futures tracking the benchmark S&P 500 and the tech-heavy Nasdaq 100 indexes fell early on Tuesday as concerns mounted that the U.S.-Iran impasse could keep oil prices elevated for longer.

At 5:36 a.m. ET, Dow E-minis slipped 11 points, or 0.16%, S&P 500 E-minis were down 12.75 points, or 0.18%, and Nasdaq 100 E-minis fell 141.25 points, or 0.51%.

A U.S. official said President Donald Trump was unhappy with the latest Iranian proposal ​on resolving the conflict in the Middle East, pouring cold water on hopes for a resolution that had sent the S&P 500, the Nasdaq 100 and the Nasdaq Composite to record highs in recent days.

The pullback underscores how strongly the war is shaping market sentiment even during the busiest week of the U.S. corporate earnings season this quarter.

Oil prices are 54% higher than pre-war levels as the crucial shipping route through the Strait of Hormuz remains disrupted.

"The divergence between equity market optimism and the more cautious signals from bond and oil markets reinforces the view that geopolitical developments remain an active and important variable in risk management," said Ameriprise Financial's Chief Market Strategist Anthony Saglimbene.

Separately, the Wall Street Journal reported that OpenAI had missed internal targets for weekly users and revenue.

Shares of Oracle, whose reliance on OpenAI for its cloud computing ambitions has been under scrutiny, fell 4.6% in the premarket session.

Chip stocks also dropped, with Nvidia, AMD and Arm Holdings down 1.2%, 3.2% and 6.8%, respectively.

Investors will parse earnings from a bunch of corporate giants on Tuesday, including UPS, Coca-Cola and General Motors.

UPS was 0.7% higher, while Coca-Cola and General Motors rose nearly 1% each ahead of the results.

(Reporting by Niket Nishant in Bengaluru; Editing by Devika Syamnath)