The US defence secretary has warned that Hezbollah now has more rockets and missiles than most governments.Robert Gates accused Syria and Iran of supplying weapons of "ever-increasing capability" to the military wing of the Lebanese Shia Islamist movement.
"This is obviously destabilising for the whole region," he said following talks with his Israeli counterpart.
But Mr Gates did not say if Syria was supplying Hezbollah with Scud ballistic missiles, as Israel has alleged.
Hezbollah fought a 34-day conflict with Israel in 2006 during which more than 1,200 Lebanese people, mostly civilians, were killed. Some 160 Israeli people, most of whom were soldiers, also died.
United Nations Security Council resolution 1701, which ended the conflict, included an arms embargo on Lebanon, except for transfers authorised by the Lebanese government or UN.
'Delicate balance'
After meeting Israeli Defence Minister Ehud Barak in Washington on Tuesday, Mr Gates said Syria and Iran was "providing Hezbollah with rockets and missiles of ever-increasing capability".
"And we're at a point now, where Hezbollah has far more rockets and missiles than most governments in the world, and this is obviously destabilising for the whole region and we're watching it very carefully," he told a news conference at the Pentagon.
Mr Barak also warned that Syria was arming Hezbollah with "weapons systems that can turn or disrupt the very delicate balance in Lebanon".
But he played down the chances of war over the alleged transfers.
"We do not intend to provoke any kind of major collision in Lebanon, or vis-a-vis Syria... but we are watching closely these developments and think that they do not contribute to stability in the region."
Mr Barak also chose not to repeat the allegation, made by Israeli President Shimon Peres last week, that Syria had been smuggling "Scud missiles to Hezbollah so that it can threaten peace".
Syria strongly denied the charge, saying it believed Israel aimed "through these claims to further strain the atmosphere in the region". Lebanon's prime minister said it seemed Israel was trying to find a pretext for a military strike.
Last week, Syria's most senior diplomat in Washington, Deputy Chief of Mission Zouheir Jabbour, was summoned by the state department to be warned about its "provocative behaviour".
A senior state department official later said the US would consider the "full range of tools" available to halt any smuggling of Scuds.
