JERUSALEM, April 15 (Reuters) - Israel's repelling of a

massive Iranian drone and missile salvo was fully coordinated

with the Pentagon, which had a U.S. operational liaison officer

in the control room of the Arrow ballistic air defence system, a

senior Israeli official said.

The United States, along with Britain, France and Jordan,

helped Israel intercept the bulk of the weekend barrage and

potentially stave off escalation between the regional enemies.

At least half of the hundreds of pilotless one-way planes,

cruise missiles and surface-to-surface missiles, which Israel

said carried a total of 60 tonnes of explosives, were shot down

by Israeli warplanes and aerial shields, according to local

media.

Israeli officials said much of the work was done by their

Arrow 2 and Arrow 3 high-altitude defence systems, which were

developed jointly with the Pentagon and Boeing Co. ( BA )

Arrow's interceptor missiles cost between $2 million and

$3.5 million a piece, according to Israeli industry sources.

Moshe Patel, director of missile defence at Israel's Defence

Ministry, said Arrow and lower-altitude interceptors were synced

with counterpart U.S. systems in the region.

"The systems share information, for a joint picture of the

sky, and the sky was certainly busy," Patel told Channel 12 TV.

"Afterward, there is also coordination in battle doctrine.

An American officer sits in the control room of the Arrow

weapons system and essentially conducts the coordination with

the U.S. systems, shoulder-to-shoulder."

There was no immediate comment from U.S. Central Command,

which oversees Middle East operations. On Sunday, it said U.S.

forces destroyed more than 80 of the drones and at least six of

the ballistic missiles aimed at Israel.

Israel said 99% of all the projectiles were downed in time,

limiting the toll to injuries to one person and damage to one

military base. That surprised even Zvika Haimovitch, a retired

brigadier-general who formerly commanded Israel's air defences.

"(This was) well-synchronized and coordinated between all

the elements - the air, the ground forces - and, yes, to be

honest it is a great percentage and much more than we expected

if you would have asked me three days before," he told Reuters.

"But we need to be sure that we will be ready for the next

time because for sure there'll be a next time," he said. "We

need to take as an assumption that the Iranians will do their

homework next time and will try to challenge our systems. That

means we need to be one step before and not after our enemies."

Daniel Gold, director of weapons development at Israel's

Defence Ministry, told Channel 12 television that work was

already under way on more advanced Arrow models 4 and 5.

Arrow 3 shoots down incoming ballistic weapons above the

atmosphere, using a detachable warhead that slams into the

target in space.

The Maariv newspaper reported that Arrow 3 downed 110

missiles outside Israeli air space, at a potential cost of up to

$385 million. The Israeli military had no immediate comment on

that. Asked on Army Radio how much the interceptions had cost

Israel, Finance Minister Bezalel Smotrich said he did not know.

Mindful of the need for thrift in the face of foes on

several fronts, Israel in 2022 said it was developing a

laser-based missile shield to deliver shoot-downs as cheap as $2

each.

"I believe that the laser will be in the next few years one

of our main solutions in dealing with a variety of threats -

rockets, missiles, drones, UAVs and more," Haimovitch said.

(Writing by Dan Williams; Editing by Kevin Liffey)