Progress has been made in the past 24 hours in the negotiations between the U.S. and Iran, though reaching a ceasefire deal by U.S. President Donald Trump's 8pm ET deadline still looks like a long shot, a U.S. official, an Israeli official and two other sources with knowledge of the talks told U.S. news portal Axios.

The White House denied Tuesday that remarks by Vice President JD Vance about military operations in Iran had contained any suggestion of a U.S. nuclear strike against the Islamic republic.

U.S. President Donald Trump warned "a whole civilization will die" in Iran if the country does not heed his midnight cutoff to open the Strait of Hormuz, as Tehran reported U.S.-Israeli attacks on its infrastructure were already underway.

U.S.-Israeli strikes have hit the key Iranian oil export terminal of Kharg island, media reported Tuesday.

"The American-Zionist enemy has carried out several attacks on Kharg island, and several explosions have been heard there," Iran's Mehr news agency reported.

One gunman was killed and two others were wounded in a shootout with police outside the Israeli consulate in Istanbul on Tuesday, the local governor said, adding two officers were lightly wounded.

Turkish public broadcaster TRT had previously reported that two of the three attackers had been killed.

Iran's Revolutionary Guards on Tuesday warned they would retaliate beyond the Middle East and deprive Washington and its allies of oil and gas if the United States crossed "red lines", a statement carried on state television said.

"The Revolutionary Guards once again declare that if the American terrorist army crosses the red lines, our response will go beyond the region," the statement said.

An Iranian official early Tuesday issued a video message calling on youths of the Islamic Republic to form “human chains” around power plants in the country ahead of threatened strikes by U.S. President Donald

Alireza Rahimi, identified by Iranian state television as the secretary of the Supreme Council of Youth and Adolescents, issued the video call in a newscast.

Iran showed no sign of backing down Tuesday as a U.S. deadline loomed for it to reopen the Strait of Hormuz, defying threats by President Donald Trump to "decimate" the country's civilian infrastructure.

The Iranian army dismissed what they called Trump's "arrogant rhetoric and baseless threats", saying they would not hinder operations against U.S. and Israeli forces more than five weeks into the war.

U S. President Donald Trump doubled down Monday on his threat to wreck Iran's civilian infrastructure, warning U.S. forces could destroy every bridge and power plant in the country within four hours and that a truce proposal from international mediators was not yet enough.

Five weeks into the Middle East war triggered by a joint U.S.-Israeli air assault on Tehran, the U.S. leader has demanded that Iran reopen the Strait of Hormuz to international shipping by midnight GMT on Tuesday, or face a newly devastating round of bombing.

Israeli Defense Minister Israel Katz announced on Monday that Israel had conducted a "powerful strike" on Iran's largest petrochemical complex, with the operator saying it was assessing the damage from the attacks.

The complex in the Pars region services Iran's South Pars natural gas field -- the largest known gas reserve in the world -- which it shares with Qatar, and which Israel had previously hit last month.