Iran"s top national security official said Tehran would not surrender or let up on retaliatory strikes and vowed to hold President Trump responsible for killing Ayatollah Ali Khamenei.

　　Ali Larijani, the head of Iran"s Supreme National Security Council and a close confidant of Ayatollah Khamenei, said Iran was determined to avenge the killing of the leader. Larijani said the US "must pay the price," according to The New York Times on Sunday.

　　According to the Strategic and International Studies (CSIS), the operation also comes with a hefty price. The first 100 hours of Operation Epic Fury are estimated to have cost $3.7 billion, about $891 million a day, with most of the spending not budgeted for, according to the Center.

　　And The Washington Post also noted an intelligence report conducted by the US National Intelligence Council found that even a "large-scale" US-led assault on Iran was unlikely to topple the country"s government.

　　The findings raise doubts about the Trump administration"s claim that the war can be concluded within four to six weeks, the Post said, citing three unnamed sources familiar with the contents of the intelligence assessment.

　　"An external attack is more likely to strengthen that apparatus than dissolve it, enabling the IRGC to recast itself as the protector of the nation. In such a scenario, even the most determined regime critics can be swept into nationalist solidarity," read a New York Times opinion article over the weekend, doubting that the most likely outcome of the US-Israeli bombing campaign is not the advent of liberal democracy.