At a news conference at his Doral golf club in Miami on Monday night, the US president said oil prices hadn't spiked as much as he'd feared.
Trump said the US was waiving certain oil-related sanctions to cut prices.
"We have sanctions on some countries. We're going to take those sanctions off till the Strait (of Hormuz) is up," Trump said.
He was not specific, but the US last week issued a temporary, 30-day waiver to allow for the sale of Russian oil currently stranded at sea to India to alleviate pressure on the global oil market.
Oil prices surged as much as 29 per cent on Monday to their highest since mid-2022 before paring gains to settle about seven per cent higher, and gold fell more than one per cent as the escalating Iran war squeezed world energy supplies, boosted the dollar and dampened hopes of interest-rate cuts.
A rollercoaster trading day began with Iran naming Mojtaba Khamenei as successor to his father Ali Khamenei as supreme leader, signalling that hardliners remained firmly in charge in Tehran a week into its conflict with the US and Israel.
But soaring oil prices reversed, stock markets rebounded and the dollar pared gains as global leaders addressed crude supply anxieties as Trump predicted the war could soon be over.
The expanding war with Iran led some major Middle Eastern oil producers to cut supplies on fears of prolonged disruption to shipping through the Strait of Hormuz choke point.
Brent futures LCOc1 settled up $US6.27 ($A8.94), or 6.8 per cent, to $US98.96 ($A141.09) a barrel and U.S. West Texas Intermediate crude CLc1 rose $US3.87 ($A5.52), or 4.3 per cent, to $US94.77 ($A135.12).
Prices turned negative shortly after the settlement following news of a phone call between Trump and Russian President Vladimir Putin.
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