Strikes against US forces in Iraq could have been just the beginning of a great operation across the region if the US had responded, a senior Iranian commander is reported as saying.
Quoted by state TV, Amir Ali Hajizadeh said the only fitting revenge for Gen Qasem Soleimani's killing by the US was to drive US forces from the region.
The remarks came a day after Iran fired missiles at bases housing US forces.
This was a response to Soleimani's death in a Baghdad drone strike.
But in a news conference covered by Iranian state media, Revolutionary Guards aerospace commander Brig-Gen Hajizadeh said Iran had been prepared to fire hundreds or even thousands of missiles. In the event fewer than 20 were fired.
The intention had not been to kill any US troops, he said, but the operation could have been planned in such a way that as many as 500 died in the first stage, and more if the US had responded.
"We had thought that the clash would continue for three days to one week. We had prepared a few thousands of missiles for such circumstances," he said in remarks carried by the Fars news agency.
Brig-Gen Hajizadeh also said that Iran had launched cyber attacks which had disabled US systems for tracking missiles during the strikes.
However, US officials say casualties at the bases were prevented because early warning systems worked effectively.
On Wednesday, Iranian Supreme Leader Ali Khamenei described the attacks as a "slap in the face" for the US, but said revenge was a "different issue".
Gen Soleimani was widely regarded as Iran's second most powerful man.
As head of the Revolutionary Guards' elite Quds Force, he was an architect of Iranian policy in the Middle East.
Meanwhile the US said it was "ready to engage without preconditions in serious negotiations" with Iran following the countries' exchange of hostilities.
In a letter to the UN, it justified Soleimani's killing as an act of self-defence.