A senior Iranian official said ships violating the new zone would be sanctioned.
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.
The U.S. and Iran have nonetheless continued to exchange strikes, with the strategic Strait of Hormuz as the primary flashpoint. Trump said in August that the U.S. would launch a "crushing economic operation" to force Tehran into submission.
The Lebanese Ministry of Health said on Monday that 27 people have been killed in three days of Israeli strikes across southern Lebanon.
The agency also said that 69 people have been wounded including women, children and paramedics.
-ABC News' Ghazi Balkiz
The Iranian Foreign Ministry issued a stark warning to South Korea on Monday amid reports the government is weighting a more active role in the Strait of Hormuz.
"South Korea and other countries know that any participation in America's aggressive and interventionist actions in the region will be considered complicity in overt military aggression, will only complicate the situation, and will certainly not make shipping routes safer," Esmaeil Baqaei, a spokesperson for the ministry, said at a briefing.
"We have not taken an official stance, of course, but we have been in contact appropriately with South Korean officials through our embassy in Seoul, and we publicly warn all countries that they should be careful not to become tools for America's aggressive actions," he continued.
Later on Monday, Baqaei posted a message on X saying ties between the two countries have "consistently developed on the basis of mutual respect" and that no country should "yield to America's pressure and threats."
-ABC News' William Gretsky
The speaker of the Iranian parliament, Mohammad Bagher Ghalibaf, posted to X on Monday in response to Secretary of Defense Pete Hegseth's threat to sink Iranian oil tankers if Iran targeted the U.S. Navy.
"It's simple: the oil and gas production chain here is sprawling, accessible, and exposed," Ghalibaf said. "American oil and gas companies across these waters and facilities share that exposure. Strike our assets and you get struck. We've already proven it. Ask the bases that are no longer viable."
-ABC News' Victoria Beaule and Morgan Winsor
Iranian Foreign Ministry spokesperson Esmaeil Baqaei told reporters at his weekly press conference on Monday that a Qatari delegation was in Iran on Sunday "to help reduce tensions," and that an Iranian technical delegation had visited Qatar recently.
-ABC News' Victoria Beaule and Morgan Winsor
