Hours earlier, US Secretary of State Marco Rubio had outlined the effort that began on Monday to escort stranded tankers out of the Gulf.
The strait has been virtually shut since the conflict began, blocking some 20 per cent of world oil supplies and igniting a global energy crisis.
"We have mutually agreed that, while the Blockade will remain in full force and effect, Project Freedom ... will be paused for a short period of time to see whether or not the Agreement can be finalized and signed," Trump wrote on social media.
Shortly after Trump's post, US crude oil futures fell $US2.30 and broke below $US100 ($A138) per barrel, a much-watched threshold since the conflict sent energy prices soaring two months ago.
Rubio and other senior administration officials said earlier on Tuesday that Iran could not be allowed to control traffic through the strait.
Iran has effectively sealed off the strait by threatening to deploy mines, drones, missiles and fast-attack craft.
The United States has countered by blockading Iranian ports and mounting escorted transits for commercial vessels. The US military said on Monday it had destroyed several Iranian small boats, as well as cruise missiles and drones.
Rubio told reporters at the White House the US had achieved its objectives in its military campaign, which was launched on February 28 alongside Israel.
"Operation Epic Fury is concluded," Rubio said.
"We're not cheering for an additional situation to occur."
One of Trump's central objectives in launching military strikes against Iran was to ensure Tehran does not develop a nuclear weapon, something Tehran has denied seeking. However, Iran has not handed over more than 900 pounds of highly enriched uranium.
While Rubio was speaking, Britain's Maritime Trade Operations agency reported that a cargo vessel had been struck by a projectile in the strait.
US Defense Secretary Pete Hegseth said the US had successfully secured a path through the waterway and that hundreds of commercial ships were lining up to pass through. The four-week-old truce with Iran was not over, he added.
"Right now the ceasefire certainly holds, but we're going to be watching very, very closely," he said.
General Dan Caine, chairman of the US Joint Chiefs of Staff, said Iranian attacks against US forces fell "below the threshold of restarting major combat operations at this point".
Shortly after Hegseth spoke, the UAE's defence ministry said its air defences were again dealing with missile and drone attacks coming from Iran, though Iran's joint military command denied carrying out attacks.
The UAE's foreign ministry said the attacks were a serious escalation and posed a direct threat to the country's security, adding that the Gulf Arab state reserved its "full and legitimate right" to respond.
Iran's foreign ministry rejected Abu Dhabi's statements, saying its armed forces' actions had been solely aimed at repelling American aggression.
The US military said on Monday that two US merchant ships made it through the strait, without saying when, while shipping company Maersk said the Alliance Fairfax, a US-flagged ship, exited the Gulf under US military escort on Monday.
Iran denied any crossings had taken place.
The war has killed thousands as it has spread beyond Iran to Lebanon and the Gulf, and roiled the global economy. The head of the International Monetary Fund said on Tuesday that even if the conflict ended immediately, it would take three to four months to deal with the consequences.
Trump told reporters Iran's military had been reduced to firing "peashooters" and Tehran wanted peace, despite public sabre-rattling.
The conflict is pressuring Trump's administration ahead of crucial midterm elections in November, as rising gas prices hit voters' pockets.
Diplomatic efforts to end the conflict have yet to yield results. US and Iranian officials have held one round of face-to-face peace talks, but attempts to set up further meetings have failed.
Iranian Foreign Minister Abbas Araqchi has said that peace talks were still progressing with Pakistan's mediation. He arrived in Beijing on Wednesday and met with his Chinese counterpart underscoring close ties between the two countries shortly before Trump is scheduled to travel to meet with Xi Jinping.
with Reuters
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