The huge explosion that destroyed a major missile-testing site near Tehran three weeks ago was “a major setback for Iran’s most advanced long-range missile program,” according to “current and former” US and Israeli intelligence officials and missile technology experts quoted by the New York Times Monday.

The experts said surveillance photos showed that the Iranian base, which was almost completely leveled in the blast, was a central testing center for advanced solid-fuel missiles. Such missiles do not require a fueling process before launch and can thus be launched almost instantly. This makes them more threatening as a deterrent against pre-emptive attacks by Israel or the United States, because they can be fired back at the attacker before the attacker can destroy all of them.

They are also better suited than older liquid-fuel designs for carrying warheads long distances.

It is still unclear what caused the explosion, but both American and Israeli officials “showed little curiosity about its cause,” the Times reported. “Anything that buys us time and delays the day when the Iranians might be able to mount a nuclear weapon on an accurate missile is a small victory,” one Western intelligence official who has been deeply involved in countering the Iranian nuclear program told the newspaper. “At this point, we’ll take whatever we can get, however it happens.”