The leader of Lebanon's militant Hezbollah movement says it has acquired sophisticated rockets despite Israel's efforts to prevent it obtaining them.
Hassan Nasrallah told supporters it did not matter what the Israelis did to try to cut supply routes because the group already possessed "precision rockets".
He did not produce evidence of this.
Israel, which in 2006 fought a war with Hezbollah, has conducted air strikes in Syria aimed at stopping Iran supplying its ally with advanced weaponry.
On Monday night, a Russian military reconnaissance IL-20 plane was accidentally shot down by Syrian air defence forces responding to a raid by Israeli jets on a Syrian military facility in the Mediterranean city of Latakia.
Russia blamed Israel for the incident, in which all 15 members of the plane's crew were killed. Israel expressed sorrow for the deaths, but said responsibility for them lay with the Syrian military, as well as with Iran and Hezbollah.
Russia, Iran and Hezbollah have helped turn the tide of Syria's civil war decisively in favour of President Bashar al-Assad in the past three years.
In a televised speech on Wednesday night, Hassan Nasrallah rejected Israel's assertion that it had attacked the military facility in Latakia to prevent the transfer on behalf of Iran to Hezbollah of systems to manufacture accurate weapons.
He claimed that Israel was using Hezbollah and Iran as an "excuse".
"Israel is working on preventing Syria from possessing missile capabilities to guarantee it a balance of terror," he said.
In another speech on Thursday morning, the Hezbollah leader declared that the dozens of Israeli strikes aimed at preventing it from acquiring rockets with highly accurate targeting capacity had failed because it had "already been achieved".
"No matter what you do to cut the route, the matter is over and the Resistance possesses precision and non-precision rockets and weapons capabilities."
"If Israel imposes a war on Lebanon, Israel will face a fate and a reality it has never expected on any day," he warned.
Israel's Defence Minister, Avigdor Lieberman, meanwhile insisted that it would continue to target Iranian activities in Syria despite Monday's incident.
"We will do everything, everything that is required, in order to defend the security of Israeli citizens. On this issue we have no other alternative," he told Army Radio.
Mr Lieberman also said that Israel would fully co-operate with a Russian investigation into the downing of its plane, adding: "We have nothing to hide. We acted as we always act."
Although Russian President Vladimir Putin acknowledged on Tuesday that there had been "a chain of tragic, accidental circumstances", he did complain to Israeli Prime Minister Benjamin Netanyahu that "Russian-Israeli agreements on preventing dangerous incidents had not been observed".