The Dow Jones industrial average rose 0.8 percent, the broad-based S&P 500 index rose 1 percent and the tech-heavy Nasdaq composite index rose 1.2 percent.
Concerns about oil supplies during the Iran war are bubbling up. But this weekend, plans to release 400 million barrels of crude oil from various countries' reserves became concrete.
At the same time, there were reports that Iran had begun allowing cargo ships to pass through the Strait of Hormuz.
The price of North Sea oil fell back slightly, to around $100 per barrel.
AI company OpenAI said talks are underway with other players about a collaboration worth $10 billion.
The index-heavy semiconductor giants Broadcom, Nvidia and AMD rose between 0.9 and 1.7 percent.
