"Today our people and our armed forces are ready to defend their goals anywhere," Ayatollah Ali Khamenei told a ceremony for the elite Revolutionary Guards carried on state television.
"This divine force has answered all threats, and we are witnessing today that this divine force is now doing the same for the Lebanese and the Palestinian people," he added in the ceremony to bring the Shahab-3 missile into service.
In Jerusalem, Israeli foreign ministry spokesman David Saranga told AFP that the new missile "is a threat not only to Israel but to the whole region and also to Europe."
Television pictures showed Khamenei flanked by officers and other clerics, at least 1,000 troops in ceremonial dress, and three of the Shahab-3 rockets on what appeared to be mobile launchers.
The report said the Revolutionary Guards, the hardline ideological spearhead of the regime who have their own air force and navy, were also given some new but unidentified attack and transport helicopters as well as an undisclosed number of Russian-built Sukhoi-25 jets.
Yahya Rahim-Safavi, the head of the Revolutionary Guards, said in his speech during the ceremony in Tehran that his force was now "ready to defend Iran against any threat".
Iran's foreign ministry reported earlier this month a final test of the Shahab-3, which brings arch-enemy Israel well within range of the country's armed forces.
Officials here have previously said the missile -- based on North Korea's No-Dong and Pakistan's Ghauri-II -- has a range of 1,300 kilometersmiles). It can reportedly carry a warhead weighing up to 1,000 kilogrammes (2,200 pounds).
In Farsi, Shahab means "meteor" or "shooting star".
That announcement sparked alarm in the Jewish state, which along with the United States alleges that Iran is using an atomic energy programme as a cover for secret nuclear weapons development.
Khamenei's comments about defending the anti-Israeli cause is also likely to increase concerns in Israel, which accuses Iran of funding its hardline militant enemies.
While the testing and inauguration of the missile was in itself expected to come at some point, the timing of the events has raised eyebrows in diplomatic circles.
Iran is currently under mounting international pressure over its suspect nuclear programme, and facing demands from International Atomic Energy Agency (IAEA) director Mohamed ElBaradei to allow surprise inspections of suspect facilities.
The IAEA has been urging Iran to immediately sign, ratify and implement an additional protocol to the nuclear Non-Proliferation Treaty (NPT) that would allow its teams to drop in on sites of interest at short notice.
So far the Vienna-based UN body is only allowed to pay pre-arranged visits to declared sites, but during a visit here this month ElBaradei did secure a pledge from Iran to discuss the matter further.
There have also been reports, quoting anonymous diplomats, that IAEA inspectors -- who began a fresh round of site visits on Saturday -- had discovered evidence that suggested Iran could have begun enriching uranium.
But speaking to reporters here Sunday, government spokesman Abdollah Ramazanzadeh said he was not rattled by such reports being released in the countdown to ElBaradei's next report on Iran in September.
"We are not worried about the IAEA's report," he said, describing speculation over the inspector's findings as "a new wave of psychological warfare" against Iran.
He added: "I deny that we have enriched uranium."