If the Israeli assertion is correct, Damascus has boosted the Iranian-backed Hezbollah's already vast arsenal of missiles with the short-range ballistic Scuds, which can reach just about every corner of the Jewish state.
That would mark an ominous shift in the regional balance of power against Israel and that could give it pause for thought over its threat to launch pre-emptive strikes against Iran's nuclear infrastructure.
If such attacks were launched, Iran would undoubtedly retaliate, calling on its proxies Hezbollah and the Palestinian Hamas in the Gaza Strip, not to mention its key ally Syria, to unleash unprecedented broadsides of missiles against Israel to supplement its own Shehab-3 ballistic missiles.
Syria has denied the Israeli accusation. Lebanese Prime Minister Saad Hariri has too, likening the Israeli allegation to the U.S. charges that Saddam Hussein had weapons of mass destruction in 2003.
Hezbollah has said its weapons are none of Israel's business.
The Syrian and Hezbollah responses were to be expected. But Hariri's denial is more problematical -- and ominous.
The Sunni prime minister has no love for the Shiite Hezbollah. It crushed his loyalists and allies in a weeklong May 2008 bloodbath in which 100 people perished, an action that almost plunged Lebanon back into civil war.
Hariri had long blamed Syria for the 2005 assassination of his father, former Prime Minister Rafik Hariri. That killing forced Syria to withdraw its military from Lebanon amid an international outcry.
But the Syrians have steadily restored their former influence over their tiny neighbor, apparently with the blessing of the U.S. administration of President Barack Obama, who wants Damascus to break with Iran.
This resulted in the younger Hariri, who jeopardized U.S. support when he bowed to pressure to take Hezbollah into his government in 2009, having to make the humiliating journey to Damascus in December to bow to Syrian domination.
In that light, his denial that Syria shipped Scuds to Hezbollah has a hollow ring to it. He doesn't want his country flattened by the Israelis but Syria may be insisting he deny the Israeli claim.
That said, Washington hasn't confirmed that Hezbollah has received any Scuds and this ambivalence about the whole affair casts some doubt on the Israeli claim.
This suggests the Obama White House sees Iran and its alleged drive for nuclear weapons as the greater threat in the Middle East and doesn't want a new conflict between Israel and Hezbollah, and probably Syria as well, to distract from what it sees as the main task of defanging Tehran.
Military analysts suspect that, amid the Middle East's complex web of intrigue, the hard-line Israeli government of Prime Minister Binyamin Netanyahu seeks to torpedo a U.S. rapprochement with Syria, long one of Israel's most implacable foes.
That's not as fanciful as it sounds, since such a rapprochement would intensify pressure on Netanyahu to revive the moribund peace process as Obama wants.
Some military analysts doubt that with tensions so high Syria, whose military is in poor shape, would risk war with Israel.
Nor, they argue, would Hezbollah want to lumber its agile forces with cumbersome Cold War-era liquid-fueled Scuds that require up to 45 minutes to fuel and can only be launched from erector trucks that are easily detectable by Israeli reconnaissance aircraft and drones that keep Lebanon under surveillance round the clock.
Israeli Defense Minister Ehud Barak estimated in March that Hezbollah has 45,000 rockets and missiles, nearly four times the number it had during its 2006 war with Israel.
These include the Syrian-engineered M-600 missile with a range of 160 miles, enough to reach Tel Aviv, and an internal guidance system that makes it more accurate than most of Hezbollah's systems.
Jane's Defense Weekly reported in October that Syria had supplied these to Hezbollah.
The Scud, says the U.S. global security consultancy Stratfor, "runs counter to everything Hezbollah has learned from fighting the Israelis -- guerrilla resistance, hidden weapons caches and the lighter more mobile and more concealable artillery rockets that characterized its success in 2006.
"Therefore we find it difficult to believe Israel's claim of operational Scuds being transferred to Hezbollah in Lebanon."