The United States said Tuesday it had not determined if Syria transferred Scud missiles to Hezbollah militants based in Lebanon.
State Department spokesman Philip Crowley commented Tuesday, a day after his department summoned a top Syrian diplomat to protest potential missile transfers.
Crowley says the U.S. is still looking into whether any transfers took place. He said arming Hezbollah would represent a significant threat to regional security.
The State Department says officials questioned Deputy Chief of Mission Zouheir Jabbour, the highest-ranking Syrian present in Washington.
State Department spokesman Gordon Duguid said it was the fourth time in recent months that U.S. officials have raised concerns to the Syrian embassy.
Israel has accused Syria of delivering missiles to Hezbollah to threaten Israel. Syria's foreign ministry has denied the charges, saying Israel is looking for an excuse to attack.
Lebanese media reports say Prime Minister Saad Hariri has compared Israeli allegations that Hezbollah has Scud missiles to allegations about Iraqi weapons before the 2003 U.S.-led invasion.
He says he believes the Israeli allegations were intended to destabilize Lebanon ahead of the tourist season.
Israel and Hezbollah fought a month-long war in 2006 that killed more than 1,200 Lebanese and about 160 Israelis. During the war, Hezbollah fired thousands of missiles into Israel, and Israeli forces carried out attacks on Lebanese territory.
The United States has recently made overtures to Syria, including nominating the first U.S. ambassador to Damascus since 2005. Washington withdrew its last ambassador after the assassination of former Lebanese President Rafik Hariri. Many countries blame the killing on Syria.
Some information for this report was provided by AP, AFP and Reuters.