The Obama administration could decide this week to approve lethal aid for Syrian rebels, officials said.
It will also consider the merits of a less-likely move to send in US air power to enforce a no-fly zone over the civil war-torn nation.
White House meetings are planned over the coming days as Syrian president Bashar Assad's government forces are apparently poised for an attack on the key city of Homs, which could cut off the armed opposition from the south of the country and clear a path for the regime from Damascus to the Mediterranean coast.
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. Opposition leaders have warned Washington that their rebellion could face devastating, irreversible losses without greater support.
US secretary of state John Kerry postponed a planned trip to Israel and three other Middle East countries to participate in White House discussions, said officials. They said Barack Obama was leaning closer towards signing off on sending weapons to vetted, moderate rebel units.
The US has spoken of possibly arming the opposition in recent months but has been hesitant because it does not want al Qaida-linked and other extremists fighting alongside the anti-Assad militias to end up with the weapons. White House spokeswoman Bernadette Meehan said Mr Obama's advisers were considering all options to hasten a transition in Syria. "The United States will continue to look for ways to strengthen the capabilities of the Syrian opposition," she said.
President Obama has already ruled out any intervention that would require US troops on the ground. But other options such as deploying air power to ground the regime's jets, gunships and other aerial assets are now being more seriously debated, the officials said, while warning that a no-fly zone or any other action involving US military deployments in Syria were far less likely right now.
The President has declared chemical weapons use by the Assad regime a "red line" for more forceful US action. American allies including France and Britain have said they have determined with near certitude that Syrian forces have used low levels of sarin in several attacks. The US officials said responses considered in this week's meetings concern the deteriorating situation on the ground in Syria, independent of final confirmation of possible chemical weapons use.
Any intervention would bring the US closer to a conflict that has killed almost 80,000 people since Assad cracked down on protesters inspired by the Arab Spring in March 2011 and sparked a war that has been increasingly defined by sectarian clashes between the Sunni-led rebellion and Assad's Alawite-dominated regime.
Intervention would essentially pit the United States alongside regional allies Saudi Arabia, Turkey and Qatar in a proxy war against Iran, which is providing much of the materiel to the Syrian government's counter-insurgency and, through Hezbollah, more and more of the manpower.