Iran has warned it will target any U.S. warships attempting to enforce an alternative shipping route through the Strait of Hormuz, escalating tensions as diplomatic efforts to ease the crisis remain uncertain.

Mohsen Rezaei, a senior adviser to Iran’s Supreme Leader, said Monday that Tehran would not permit any maritime corridor other than the route it has designated for vessels transiting the strategic waterway.

“We won’t allow the second corridor to open. Even if they deploy warships, we will target them,” Rezaei said in an interview with Iranian state media.

He also warned that Iran would respond militarily if the United States maintained what Tehran describes as a naval blockade.

“There will certainly be serious dangers to U.S. ships and bases. We will not sit and watch the U.S. continue the naval blockade,” Rezaei said.

The remarks came as U.S. President Donald Trump said he expected negotiations with Iran to begin within the next day or two after previously describing the planned talks as Tehran’s “last chance” to reach an agreement before facing further military action.

Iran, however, denied that new negotiations with Washington were underway.

Foreign Ministry spokesperson Esmail Baghaei said the Islamic Republic is currently engaged only in discussions with Oman concerning a temporary shipping arrangement through the Strait of Hormuz.

Baghaei also reiterated Tehran’s position that the strategically important waterway will remain closed until what he called U.S. violations come to an end.

Before the conflict erupted, roughly one-fifth of the world’s traded oil and liquefied natural gas passed through the Strait of Hormuz, making it one of the world’s most critical maritime trade routes.

Meanwhile, maritime security concerns intensified after a cargo vessel sailing through the Strait of Hormuz was struck by what British authorities described as an “unknown projectile.”

The United Kingdom Maritime Trade Operations (UKMTO) said the incident occurred about 37 kilometers (23 miles) northeast of Al Khasab, Oman.

The agency did not identify the vessel or provide immediate details about possible casualties or the extent of the damage, but confirmed that an investigation had been launched.

The latest threats and maritime incident underscore the fragile security situation in the Gulf as tensions between Iran and the United States continue to raise concerns over global energy supplies and international shipping.