Iran is ready to let Japanese-related vessels pass through the Strait of Hormuz, Japanese media reported, citing Iranian Foreign Minister Abbas Araqchi.
The countries have started talks about possibly opening the strait, a vital artery for global oil supplies, Araqchi told Japan's Kyodo News in a phone interview on Friday.
Japan's foreign and trade ministries and the Prime Minister's Office however did not respond to calls from Reuters on Saturday seeking further comments on the report.
The Strait of Hormuz, a conduit for around a fifth of global oil and liquefied natural gas supplies, has been effectively closed to most shipping since the United States and Israel launched the war against Iran almost three weeks ago.
Japan gets around 90 per cent of its oil shipments via the strait, which Iran has largely closed since the start of the war.
A spike in global oil prices sparked by the war, which entered its fourth week on Saturday, has prompted Japan and other countries to release oil from their reserves.
US President Donald Trump met Japanese Prime Minister Sanae Takaichi on Thursday, urging her to "step up" as he presses allies — so far unsuccessfully — to send warships to help open the strait.
Takaichi told reporters after the Washington summit that she had briefed Trump on what support Japan could and could not provide in the strait under its laws.
Japan's actions are limited under its postwar pacifist constitution, but 2015 security legislation allows Japan to use force overseas if an attack, including on a close security partner, threatens Japan's survival and no other means are available to address it.
US sending additional troops to region
Despite Trump saying on Friday that the US was considering "winding down" military operations against Iran, its military is deploying thousands of additional troops to the Middle East,
Three US officials told Reuters that 2,500 Marines, along with the USS Boxer, an amphibious assault ship, and accompanying warships, would be deployed to the region, although they did not say what their role would be.
No decision had been made to send troops into Iran itself, two of the officials told Reuters, but the military will build up the capacity for potential future operations in the region.
One of the officials, who spoke on condition of anonymity, said the troops were departing the west coast of the United States about three weeks ahead of schedule.
The additional deployments will add to the 50,000 US troops already in the Middle East and would bring two Marine Expeditionary Units to the region.
The US has carried out strikes against 7000 targets inside Iran and hit more than 40 Iranian mine-laying vessels and 11 submarines, the Pentagon says.
Khamenei shares New Year's message
Meanwhile, Iran's newly instated supreme leader, Mojtaba Khamenei, has thanked the Iranian people for their resistance as the war hit the three-week mark.
A speech attributed to Khamenei, who has not been seen in public since an Israeli attack that killed his father and predecessor on the war's first day, was read out on state television on Friday for Nowruz, the Persian calendar's new year, which began over the weekend.
Khamenei thanked the president, the government, the armed forces and the Iranian people for their resistance against the joint US-Israeli attacks.
The adversaries were not relying solely on military means such as missiles, drones and torpedoes, he said, adding that Iran's "front line" was broader than its enemies wished to acknowledge.
Khamenei declared Nowruz to be the "year of the resistance economy in the spirit of national unity and security".
The supreme leader's message also urged all media outlets to exercise restraint and avoid highlighting vulnerabilities, warning that doing otherwise could help the enemy achieve its objectives.
He also denied that Iranian forces had carried out attacks on Turkey and Oman.
"The enemy believed that by targeting the leader (Ayatollah Ali Khamenei) and influential figures, it could instil fear and force the people to withdraw," Khamenei said in a Nowruz message on his Telegram channel.
"But the nation responded with unity ... resistance, and dealt a disorienting blow to the enemy."
Iran attacks oil refinery, Israel kills IRGC member, pledges further strikes
In other developments, Iran attacked an oil refinery in Kuwait on Friday and Israel killed a spokesperson of Iran's Islamic Revolutionary Guard Corps (IRGC).
Israel promised to avoid further attacks on Iran's South Pars gas field the day after an Iranian retaliatory strike on Qatar caused damage that will leave the world short of natural gas for years to come.
Israel's military said it had attacked government facilities in Tehran.
Iranian state TV said Ali Mohammad Naini, deputy head of public relations for the Islamic Revolutionary Guard Corps, was the latest of dozens of leading government and military officials to be assassinated by Israel.
In Tel Aviv and Jerusalem, air raid sirens howled as explosions from interceptors rang out.
The military said Iran had fired a barrage of missiles, and the ambulance service said at least one appeared to have carried dispersing cluster bombs.
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