Crude futures hovered close to multiyear highs on Tuesday, as investors awaited Trump's announcement at 2 p.m. ET.
The prospect of the U.S. withdrawing from the landmark agreement to limit Iran's nuclear program, formerly known as the Joint Comprehensive Plan of Action, has ramped up energy market fears of an imminent supply shock.
"The geopolitical consequences of a possible dismantling of the JCPOA would likely to play a larger and long-lasting role in pushing oil prices higher than short-term policy uncertainty," Michael Cohen, Barclays director of energy market research, said in a research note Monday.
Trump is likely to either announce he will not be renewing a waiver on Iranian sanctions or reaffirm his firm opposition to the global pact, Barclays said. Regardless of Tuesday's announcement, Cohen predicted the current Iran nuclear deal would "not survive under President Trump."
"And in the next couple of years, this more hawkish foreign policy could fuel already elevated tensions in the Middle East, specifically in Iraq, Syria, and Yemen, as the hostilities between Iran and Saudi Arabia escalate," Cohen added.
Trump, a fervent critic of the accord, has long threatened to walk away from the landmark deal signed by Iran, the Obama administration, Russia, China, Britain, France, Germany and the European Union. Trump has complained the "insane" agreement does not restrict Iran's nuclear activities for long enough and fails to stop the country's development of ballistic missiles.
In response, Iranian President Hassan Rouhani has said Trump has "no right" to renegotiate the deal and accused him of "maliciously violating" its conditions.
A dramatic uptick in crude futures over recent months has partly been driven by mounting expectations that the world's largest economy could soon pull out of the agreement.
Ahead of the Trump administration's decision, Brent crude traded at around $75.38 on Tuesday morning, down 1 percent while U.S. West Texas Intermediate futures stood at $69.85, off around 1.2 percent.
Alongside OPEC-led production cuts, robust demand for crude has helped diminish a global supply overhang in recent months and left the energy market more exposed to shocks.
Iran's oil production has rebounded to nearly 4 million barrels a day since world powers opted to ease sanctions over its nuclear program. However, external observers have warned that reimposing sanctions could reduce Iranian oil exports by up to 1 million barrels a day — just the type of supply shock that could be price supportive.
"We would expect an inevitable jump in oil prices should the sanctions return," Cliff Kupchan, chairman of Eurasia Group, a Washington-based political consulting firm, said in a research note.
"We return to the possibility that the president's looming verdict may — to a significant extent — be a negotiating ploy and hence should not be considered a final verdict on the deal. … Trump is regularly underestimated, and it's not over."