Two Iranian boats approached and fired on a tanker off Oman’s coast on Saturday morning, the U.K. Maritime Trade Operations organization said.

The Islamic Revolutionary Guard Corps ships were said to have approached a tanker about 20 nautical miles off the northeastern coast of Oman, according to the UKMTO, a maritime security monitoring group.

"The Master of the Tanker reports being approached by 2 IRGC gun boats, no VHF challenge that then fires upon the tanker," UKMTO said, describing a typical emergency vessel-to-vessel radio communication or "challenge."

The tanker and its crew were reported safe, UKTMO said, adding that an authorities were investigating.

The Strait of Hormuz "has returned to its previous state," Iranian state TV reported on Saturday, quoting a spokesperson for the Iranian Armed Forces.

The spokesperson said Tehran had previously allowed the managed passage of a limited number of oil tankers and commercial vessels "in good faith" following recent negotiations, Iran state TV IRIB reported.

The spokesperson accused the United States of failing to uphold its commitments and continuing "piracy and maritime robbery under the so-called blockade."

"As a result, control of the Strait of Hormuz has returned to its previous state," the spokesperson reportedly said, adding that the strategic waterway is now under "strict management and control" by Iran's military.

The current Iranian negotiations leader, Mohammed Ghalibaf, the speaker of the Iranian Parliament, posted a statement to social media Friday evening stating President Donald Trump "made seven claims in one hour, all seven of which are false."

Ghalibaf's statement also echoes what Foreign Ministry spokesperson Esmael Baqaei said earlier -- that Iran would not allow navigation in the Strait of Hormuz if the American blockade continued, and that navigation will be carried out based on a "designated route" and with "Iranian permission."

He added that the "open or closed status of the Strait and the regulations governing it will be determined by the field, not social media."

The statement went on to say: "Media warfare and public opinion engineering are an important part of the war, and the Iranian nation will not be affected by these tricks."

-ABC News' Victoria Beaule

President Donald Trump said in-person discussions would "probably" happen this weekend. Though two U.S. officials see Monday as the first feasible day that a second round of negotiations could take place in Islamabad. They also note that timing and the delegations are not locked in yet.

Trump has said that Iran has agreed to suspend their nuclear program indefinitely. Though there's still no agreement on how long Iran would suspend uranium enrichment or the terms around that, according to U.S. officials and another source familiar with the state of play. This is the key sticking point.

On Iran's stockpile of highly enriched uranium, a U.S. official says negotiators are discussing multiple ways to address the issue in part because it's possible that not all of it can be downblended within the country, as some might not be stable enough to undergo the process.

The official says there are many details on this front to work out, but that the administration believes the sides are fundamentally in agreement.

At present, Iran's missile program and its support for regional proxies are not being discussed as terms within the potential memorandum of understanding, a U.S. official and another source familiar with the talks said.

-ABC News' Shannon K. Kingston

The Trump administration has announced sanctions against seven commanders of Iraqi militias backed by Iran that have "planned and directed attacks against U.S. personnel, facilities, and interests in Iraq," according to the U.S. State Department.

"These individuals lead some of the most reprehensible Iran-backed terror groups in Iraq — Kata’ib Hizballah, Kata’ib Sayyid Al-Shuhada, Harakat Al-Nujaba, and Asa’ib Ahl Al-Haqq," according to the State Department. "These militias not only threaten American lives but also undermine Iraq’s sovereignty, exploit its resources to fund terrorism, and attack Iraq’s neighbors and innocent Iraqi civilians with impunity."