Traders work on the floor of the New York Stock Exchange (NYSE) at the opening bell in New York. AFP
Iran Foreign Minister Abbas Araghchi said the Strait of Hormuz will remain "completely open" as long as a ceasefire in the Middle East lasts, addressing a supply disruption that had pushed oil prices above $100 a barrel and sparked recession worries.
About 20 minutes into trading, the Dow Jones Industrial Average was up 1.2 percent at 49,144.70.
The broad-based S&P 500 climbed 0.6 percent to 7,085.42 while the tech-rich Nasdaq Composite Index advanced 0.9 percent to 24,312.25.
Major US indices have closed at records the last two days in anticipation of a US-Iran peace agreement.
"The thought that the war could end soon has translated into a sharp drop in oil prices and a calming of concerns about a prolonged global economic slowdown," said Briefing.com analyst Patrick O'Hare.
"In turn, it has put the focus back on the earnings outlook, which is being viewed with rose-colored glasses."
But among individual companies, Netflix slumped 10.5 percent as some analysts expressed dissatisfaction with the company's forecasts.
The streaming giant's co-founder Reed Hastings announced he is stepping down as chairman when his term ends in June.
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