The Strait of Hormuz remains a flashpoint with peace talks stalled.
President Donald Trump announced "major combat operations" against Iran on Feb. 28, with massive joint U.S.-Israeli strikes targeting military, government and infrastructure sites.
Delegations from the U.S. and Iran entered negotiations in June aimed at a war-ending deal based on a memorandum of understanding signed by both countries.
Those talks broke down as the U.S. and Iran continued to exchange strikes, with the strategic Strait of Hormuz as the primary flashpoint. Trump then said in August that the U.S. would launch a "crushing economic operation" to force Tehran into submission.
The United Kingdom Maritime Trade Operations (UKMTO) Centre reported that a tanker was "struck by an unknown projectile" in the Strait of Hormuz on Monday morning, with at least two crew members injured.
"The vessel is reported to be continuing to its next port of call under its own power. There is no reported environmental impact at this time," the UKMTO said in its alert.
Iranian forces are prepared to launch a "counteroffensive" in the event of renewed U.S. attacks on the country, Islamic Revolutionary Guard Corps spokesperson Brig. Gen. General Hossein Mohebbi told the semi-official Tasnim News Agency in an interview published on Monday.
"If a new aggression takes place, there will definitely be significant changes in our defense and our counteroffensive," Mohebbi said. "We will definitely change the geography of the war," he added.
The spokesperson said Tehran also plans to use new weapons and tactics in the event of renewed fighting. "We will definitely bring new weapons with new capabilities into the battlefield, and the world will be surprised," he said.
The U.S., Mohebbi said, has already suffered a "historic and disgraceful defeat."
Iranian parliament speaker Mohammad Bagher Ghalibaf said on Sunday that Tehran will not allow the reopening of the Strait of Hormuz until all of its conditions have been met.
"Over the past seven months, we have shown that we are not helpless in the face of aggression," Ghaliaf said in a statement published by the semi-official Fars News Agency.
"We must both fight and negotiate," said Ghalibaf, who led the Iranian negotiating delegation to Islamabad in April.
"Our messages have been conveyed and our conditions have been clearly explained to the other side through mediators, and the enemy knows very well that the path of deception and one-sided imposition is closed," Ghalibaf continued.
"Until these conditions are met, the legitimate rights of the Iranian people are recognized and the Americans fulfill their commitments, there will be no opening for a return to the previous conditions for negotiations or for the Strait of Hormuz to be opened," he said.
"Today, the old American order in West Asia has collapsed, and it is the Islamic countries of the region that must implement a new order," Ghalibaf added.
The State Department posted a security alert on Saturday evening advising Americans currently in the Middle East to "exercise heightened vigilance" and "be aware of potential flight cancellations, airspace closures, and travel disruptions."
"Iranian-supported Houthis have engaged in hostilities against Saudi Arabia, including civilian airports. This military conflict has the potential to escalate rapidly," the post said.
The alert also advised Americans outside the Middle East to "seriously reconsider travel to and through the region."
-ABC News' Lauren Minore
