The United States summoned a senior Syrian diplomat Monday and demanded an "immediate" end to arms transfers to Hezbollah, criticizing any such shipments as an impediment to peace.

"The most senior Syrian diplomat present in Washington today, Deputy Chief of Mission Zouheir Jabbour, was summoned to the Department of State to review Syria's provocative behavior concerning the potential transfer of arms to Hezbollah," department deputy spokesman Gordon Duguid said in a statement.

He said the United States condemns the transfer of any arms, "especially ballistic missile systems such as the Scud, from Syria to Hezbollah."

"We call for an immediate cessation of any arms transfers to Hezbollah and other terrorist organizations in the region," he added.

"Syria's designation as a state sponsor of terrorism is directly related to its support for terrorist groups, such as Hezbollah."

The diplomatic quarrel is likely to put a damper on President Barack Obama's administration's year-long campaign to engage Syria, a former US foe, and energize its thwarted push for a broad Arab-Israeli peace, particularly between Israel and the Palestinians.

US Senator John Kerry, chairman of the Senate Foreign Relations Committee, visited Damascus April 1, and after a meeting with President Bashar al-Assad he described Syria as "an essential player in bringing peace and stability to the region."

Obama in February appointed the first US ambassador to Damascus in five years, a move Kerry said was "evidence that engagement with Syria is a priority at the highest levels of our government."

The Senate approved envoy Robert Ford as the new ambassador last Tuesday.

But a day later, Washington expressed alarm to Syria over its possible sale of Scud missiles to Hezbollah militants, warning it would put Lebanon at "significant risk."

Washington expressed renewed concern Saturday over possible Scud missile supplies to Hezbollah, a Lebanese Shiite militant group backed by Syria and Iran. The United States has labelled Hezbollah a terrorist organization.

Duguid warned Monday that such arms transfers "can only have a destabilizing effect on the region, and would pose an immediate threat to both the security of Israel and the sovereignty of Lebanon.

"The risk of miscalculation that could result from this type of escalation should make Syria reverse the ill-conceived policy it has pursued in providing arms to Hezbollah," Duguid said.

"The heightened tension and increased potential for conflict this policy produces is an impediment to ongoing efforts to achieve a comprehensive peace in the Middle East."

Duguid stressed this was the fourth time such concerns had been raised with the Syrian embassy in recent months.

"Our dialogue with Syria on this issue has been frank and sustained. We expect the same in return," he said.

According to Arab media and some think-tanks, Syria has been sending some of its own arsenal of Scuds to Lebanon, an allegation denied by Damascus.

Hezbollah and Israel in 2006 fought a 34-day war that killed 1,200 Lebanese, mostly civilians, and more than 160 Israelis, mainly soldiers.