Operators of the Arrow 3 battery at Palmahim air base on the Mediterranean coast cancelled the launch of its interceptor missile after it failed to lock on to a target missile fired over the sea, the sources said.
"There was a countdown to the launch and then nothing happened," one source told Reuters on condition of anonymity. "A decision was made not to waste the interceptor missile."
Arrow is among several elements of an integrated Israeli aerial shield built up to withstand potential future missile and rocket attacks by Iran, Syria or their guerrilla allies in Lebanon and Gaza.
Initially, Israel's Defence Ministry said that "within the framework of preparations for a future interception test, a target missile was launched and carried out its trajectory successfully".
However two hours later it added, in a statement, that "the conditions had not been ripe for launching an interceptor missile".
A high-ranking official within the Defense Ministry, who requested to remain unnamed, said that the conditions did not have to do with the missile interceptor itself but with external conditions relating to the test.
"The conditions were not ripe, and therefore we arranged with our partners in advance, which include members of the defense industry, American counterparts and Air Force officials, not to pass from one stage to the other and launch the target missile, according to criteria we set from the start. This decision was made with a clear mind. During experiments we behave differently than we would during operational events. The missile interceptor and the experiment itself is very expensive," said the Defense Ministry source.
Arrow 3 interceptors are designed to fly above the earth's atmosphere, where their warheads detach to become kamikaze satellites, or "kill vehicles", that track and slam into the targets. Such high-altitude shoot-downs are meant to safely destroy incoming nuclear, biological or chemical missiles.
Arrow is jointly developed by state-owned Israel Aerospace Industries (IAI) and US firm Boeing Co. Its earlier version, Arrow 2, was deployed more than a decade ago and officials put its success rate in trials at around 90 percent.
But an Arrow 2 interception test on September 9 ended inconclusively, the Defence Ministry has said. The US journal Defense News later reported that the Arrow 2 interceptor missile had missed its target.