Top aides from the State and Defence Departments, the CIA and other agencies were gathering for a "deputies meeting" at the White House. They seek to lay the groundwork for a meeting that President Barack Obama will hold with his senior national security staff, planned for Wednesday, said US officials, who weren't authorised to speak publicly on the closed-doors talks and demanded anonymity.
The White House meetings are taking place as Syrian President Bashar Assad's government forces are apparently poised for an attack on the key city of Homs, which could cut off Syria's armed opposition from the south of the country.
As many as 5,000 Hezbollah fighters are now in Syria, officials believe, helping the regime press on with its campaign after capturing the town of Qusair near the Lebanese border last week.
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Secretary of State John Kerry postponed a planned trip today to Israel and three other Mideast countries to participate in White House discussions, officials said. He may travel to the region later in the week.
While nothing has been concretely decided, US officials said Obama was leaning closer toward signing off on sending weapons to vetted, moderate rebel units. The US has spoken of possibly arming the opposition in recent months but has hesitated because it doesn't want al-Qaeda-linked militants and other extremists fighting alongside the anti-Assad militias to end up with the weapons.