"Such arms were not found. They are trying to repeat the same scenario with Lebanon."
Hariri's comments came after the US state department summoned Zouheir Jabbour, Syria's deputy chief of mission in Washington, on Monday, and accused Damascus of "provocative behaviour" in the potential supply of arms to Hezbollah.
Hezbollah, whose political power is underpinned by a well-equipped military wing, is backed by Iran and Syria.
"We call for an immediate cessation of any arms transfers to Hezbollah and other terrorist organisations in the region," a state department spokesman said.
"The transfer of these arms can only have a destabilising effect on the region, and would pose an immediate threat to both the security of Israel and the sovereignty of Lebanon."
But the US statement stopped short of confirming the alleged transfer of the long-range missiles.
The allegations could deal a new setback to long-tense Syrian-US relations, which had begun to improve after Barack Obama, the US president took office last year.
Earlier this year, Washington named a new ambassador to Damascus five years after withdrawing its top diplomat from Syria.
On Syria's part, Bushra Kanafani, the foreign ministry spokeswoman, denied the allegations and said Syria was surprised the US was adopting what she called "Israeli claims".
"This is regrettable and could deepen the gap between Damascus and Washington," she said.
Hezbollah and Israel fought a 34-day war in 2006 over the capture of Israeli soldiers that left some 1,200 Lebanese and 160 Israelis dead.
During the month-long conflict, Hezbollah fired nearly 4,000 rockets at northern Israel, including several medium-range missiles that for the first time hit Israel's third-largest city, Haifa.