US equity futures were largely flat pre-bell Monday as President Donald Trump rejected Iran's response to the US peace proposal, sending oil prices higher amid concerns that the closure of the Strait of Hormuz would be prolonged.

Dow Jones Industrial Average futures were 0.1% lower, S&P 500 futures were flat, and Nasdaq futures were 0.1% higher.

Trump said in a post on Truth Social that he found Iran's response "totally unacceptable." Iran's response had included a demand for war reparations, an end to sanctions, full sovereignty over the Strait of Hormuz, and the release of frozen Iranian assets, the country's state media had said.

Energy firm Constellation Energy (CEG) was one of the first companies to kick off earnings this week, posting higher Q1 adjusted earnings and revenue. Among the companies reporting financial results this week are Petrobras (PBR), Cisco Systems (CSCO), Alibaba Group (BABA), Applied Materials (AMAT), and Brookfield (BN).

Oil prices were higher, with front-month global benchmark North Sea Brent crude up 2.5% at $103.82 per barrel and US West Texas Intermediate crude 2.5% higher at $97.77 per barrel.

Existing home sales report, scheduled for release at 10 am ET, is expected to show an increase of 2% for April after a decline of 3.6% in the prior month, according to estimates compiled by Bloomberg.