Live updates: Iran reasserts control over Strait of Hormuz, says it's returning to 'previous state'

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.

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

President Donald Trump continued to tout the progress between the U.S. and Iran upon touching down in Phoenix on Friday, telling reporters that the two countries have had "some very good discussions."

"We've done a good job, but we'll see," Trump said.

"Talks are going on and will go on over the weekend, and a lot of good things are happening," Trump continued, adding, "That includes Lebanon, too."

Trump acknowledged that there "could" still be differences that the U.S. and Iran need to work out, despite saying earlier Friday that Iran has "agreed to everything."

"Well, there could be," Trump said when asked to respond to reports of Iran claiming the two countries still have significant differences. "Let's see what happens. If there are, we'll have to straighten it out. But I don't think there's too many significant differences."

The president also insisted that the U.S. blockade in the Strait of Hormuz will end once the U.S. and Iran sign a deal.

"When the agreement is signed, the blockade ends," Trump said.

-ABC News' Nicholas Kerr and Emily Chang