The massive U.S.-Israeli air strikes, which have killed Iran's Supreme Leader Ayatollah Ali Khamenei, entered a third day on Monday.

The Israeli military said it launched "large-scale strikes" on Tehran on Monday after Iran's Islamic Revolution Guard Corps (IRGC) launched the ninth wave of its operation, targeting U.S. military assets across the Middle East.

The IRGC claimed it had targeted the U.S. aircraft carrier USS Abraham Lincoln, but the Pentagon said the "missiles launched didn't even come close."

Iran's retaliatory attacks took their toll. The Pentagon said that three U.S. service members have been killed and five seriously wounded in the U.S. operation against Iran.

Two U.S. officials, speaking on condition of anonymity, told Reuters the U.S. service members were killed on a base in Kuwait.

Trump predicts a four-week strike 

U.S. President Donald Trump said the U.S. operations "will continue until all of our objectives are achieved. We have very strong objectives" in a six-minute video message on Truth Social, without specifying what the objectives are.

Trump said 48 senior Iranian officials have been killed in the operation and the U.S. forces have sunk nine Iranian warships and largely destroyed Iran's navy headquarters.

As for the death of U.S. service members – the first casualties of his second term – Trump said of the possibility of more U.S. casualties, "that's the way it is."

In an exclusive phone interview with Britain's Daily Mail, Trump said the military strike against Iran will take four weeks.

"It's always been a four-week process. We figured it will be four weeks or so. It's always been about a four-week process so - as strong as it is, it's a big country, it'll take four weeks - or less," the British newspaper quoted Mr Trump as saying.

In another interview with The Atlantic magazine on Sunday, Trump said Iran's new leadership wanted to talk to him and that he has agreed.

"They want to talk, and I have agreed to talk, so I will be talking to them. They should have done it sooner. They waited too long," Trump was quoted as saying.

The U.S. military expanded targets across Iran on Sunday and said it destroyed the headquarters of the IRGC. 

Iran stresses right to defend itself

Iranian Foreign Minister Seyed Abbas Araghchi told ABC News on Sunday that no country's leader has the right to tell Iran not to respond to the ongoing U.S.-Israeli massive strikes on Iran, in response to Trump's earlier warning that Iran should not retaliate.

Araghchi said Iran has every right to defend itself and the Iranian forces "are capable enough to defend our country."

Iranian President Masoud Pezeshkian said on Sunday that "Iran considers it its legitimate duty and right to avenge the perpetrators."

On the same day, Ali Larijani, the powerful head of Iran's Supreme National Security Council, warned that "today we will hit them with a force that they have never experienced before."

In Israel, an Iranian missile attack killed at least nine people and injured dozens more in the central city of Beit Shemesh on Sunday, after a death the previous day near Tel Aviv. Three people were also injured on one of the main roads of Jerusalem.

A transitional leadership council composed of Iranian President Masoud Pezeshkian, the head of the judiciary and a member of the powerful Guardian Council had temporarily assumed the duties of supreme leader following the killing of Khamenei, while a permanent successor is found for the supreme leader.

Reactions from U.S. and its allies

Back in the U.S., Hakeem Jeffries, the top Democrat in the House of Representatives, said the deaths of the U.S. servicemen were the result of a "reckless decision" and that there was no threat to "justify this type of preemptive military strikes."

A Reuters/Ipsos poll that concluded on Sunday showed 27 percent of Americans approved of the strikes, while 43 percent of the respondents disapproved and 29 percent were not sure. About nine in 10 respondents said they had heard at least a little about the strikes.

The UK, France and Germany have issued a joint statement, saying they will take steps to defend their interests and those of their allies in the region, potentially through enabling necessary and proportionate defensive action to destroy Iran's capability to fire missiles and drones at their source.

The United States and its Arab allies including Bahrain, Kuwait, Saudi Arabia and the United Arab Emirates on Sunday condemned Iran for launching a wave of retaliatory strikes on Gulf states hosting U.S. troops in a joint statement.

"The targeting of civilians and of countries not engaged in hostilities is reckless and destabilizing behavior," said the statement.

No simple answers for what's next

As the clashes entered a third day, experts are increasingly concerned that the situation could spiral into a broader crisis. Li Zixin, assistant research fellow at China Institute of International Studies, told CMG that the current conflict between the U.S., Israel and Iran is likely to escalate, with the potential for regional instability and widespread consequences. 

Li highlighted the ongoing retaliation from Iran on U.S. military assets in the region as evidence of the conflict evolving into a "multilateral crisis," threatening the broader regional security framework.

Zhou Dewu, a former deputy editor-in-chief of Ta Kung Pao, told CGTN that if the next Iranian leader is unwilling to reconcile and prefers to engage in asymmetric "terrorist tactics" to drag the U.S. into a prolonged struggle, it would be akin to opening Pandora's box, and a new wave of terrorism could be imminent.

Zhou also noted the strategic importance of the Strait of Hormuz, stating that its closure could disrupt one-fifth of global oil shipments, causing a surge in oil prices and fueling U.S. inflation. He suggested that rising oil prices could potentially trigger anti-war sentiments within the United States.

(With input from agencies)