Washington DC - President Donald Trump said Wednesday the US and Israel were in a strong position in their war with Iran, vowing that they would "continue forward" against the Islamic Republic.

Trump said prospective replacements for slain Iranian supreme leader Ayatollah Ali Khamenei "end up dead" and that Tehran's arsenal of ballistic missiles was being "wiped out rapidly."

"We're doing well on the war front, to put it mildly. Somebody said on a scale of 10, where would you rate it? I said about a 15," Trump told a gathering of tech bosses at the White House.

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"We're in a very strong position now, and their leadership is just rapidly going. Everybody that seems to want to be a leader, they end up dead."

Speaking on the fifth day of the war, Trump repeated his justifications for attacking Iran, again claiming that Tehran was on its way to obtaining a nuclear weapon.

"When crazy people have nuclear weapons, bad things happen," Trump added.

The US-Israeli attacks have come under significant criticism, with UN-mandated investigators condemning the targeted killings of Iranian officials as violations of international law.