Secretary of State Hillary Rodham Clinton says it's only a matter of time before the rebels have enough territory and organization to create such areas.
"More and more territory is being taken," Clinton said this week. "It will eventually result in a safe haven inside Syria, which will then provide a base for further actions by the opposition."
Officials are already starting to brainstorm how a safe zone might allow Washington to step up its assistance, which has been limited to humanitarian aid and nonlethal equipment such as medical supplies and communications gear.
A senior American official, speaking on condition of anonymity because he wasn't authorized to discuss the administration's thinking publicly, said the U.S. is seeing "increased unity, cohesion and better military performance" among the rebels, including greater effectiveness in coordinating attacks, which the administration sees as proof the rebels are better employing the encrypted radios supplied by the U.S.
For now, U.S. officials are standing by their assertion that they won't provide arms to Syria's anti-Assad forces or push for a no-fly zone over rebel-controlled areas. With Syria's government fighting back forcefully against opposition offensives in Damascus, Aleppo and elsewhere, it's still unclear whether the rebels could create a secure staging ground for the rebellion.
The Libyan militia that chased from power and killed Moammar Gadhafi last year had set up the city of Benghazi as a safe haven, creating a central place to meet and strategize and an entry point for supplies from NATO and Arab countries. The U.S. set up a consulate.
The discussions on Syria come as the U.S. and its international partners look for a possibly game-changing shift in the country's bloody, 16-month conflict, which began with Syrian President Bashar Assad's brutal crackdown on protesters, followed by dissenters taking up arms against the government. More than 19,000 people have been killed, according to opposition activists, and despite increased cracks in the regime's military and political stability, there remains little to suggest an imminent end to the violence.
The establishment of a safe zone would settle one issue: the lack of an actual place inside Syria for other nations to engage with the opposition on the ground and deliver supplies into the heart of the conflict.
The U.S. would be able to shift Syrian-watching officials they've deployed in places such as Jordan and Turkey into Syria. And governments such as Saudi Arabia and Qatar that have been providing weapons to the opposition would have a more direct pipeline for military assistance.
But officials cannot point to when the rebels might be able to carve out some autonomous space for themselves within Syria. The rebels remain heavily outgunned by Assad's better trained forces. And while they've been able to increase the breadth of their attacks across Syria, they've been constantly forced to cede back any temporary territorial gains they make.
Under the current circumstances, U.S. diplomatic efforts have been stymied. Russia and China have shielded the Assad regime from U.N. Security Council action three times, most recently last week. And U.S.-led efforts such as sanctions and a campaign of international isolation may have sapped Syria's government of funds, but not its resolve to crush what it regards as an armed insurgency.
In the last month, the Obama administration has spoken of the rebels' growing ability to challenge the Assad regime's military supremacy.
National Security Council spokesman Tommy Vietor noted the pace of high-level regime defections was accelerating and that the U.S. and its partners were still advocating a political transition away from four decades of dictatorship under the Assad family dynasty. The sooner that happens, he said, "the greater the chance we have of averting a lengthy and bloody sectarian civil war and the better we'll be able to help Syrians manage a stable transition to democracy."
Clinton went a step further earlier this week, offering a battlefield picture that included Syria's ragtag alliance of militia beginning to take control of parts of the country.
She said the opposition should be preparing for how it will maintain order when it controls territory.
"They have to start working on interim governing entities. They have to commit to protecting the rights of all Syrians, every group of Syrians. They have to set up humanitarian response efforts that we can also support. They've got to safeguard the chemical and biological weapons that we know the Syrian regime has," she said.
The U.S. is also preparing, though it doesn't want to call its shots. And administration officials insist that it won't be the U.S. military that creates safe zones for the Syrian opposition—as proponents of intervention such as Republican Sen. John McCain have proposed.
Since the Syrian conflict started, U.S. officials have repeatedly cited the lack of a safe zone in Syrian territory as one of several hindrances to more aggressive American assistance—from establishing a no-fly zone over parts of the country to providing weaponry to the opposition.
Other hurdles have included a lack of regional and international consensus, the opposition's disorganization and internal rivalries, the inability to get any U.N. mandate for action and a lingering sense that American or other foreign intervention might actually mean more lives lost than saved. American officials also say involvement could prompt greater instability in a powder-keg region.
The opposition has been essentially limited to hit-and-run attacks and unable to hold any major Syrian population centers. In addition, officials note that the Assad regime is unlikely to cede a city like Aleppo without the kind of fight the rebels are unable to win.
The likely result is that any territory the rebels are able to take, occupy and defend will be far from the Mediterranean coast and not well served by existing infrastructure like good roads, solid bridges, power and water. That would complicate the establishment of foreign consulates or liaison offices, said the officials, who spoke on condition of anonymity because they said planning was at an early stage and they were not authorized to discuss it publicly.
Underscoring the value some see in the safe zones, more than 60 foreign policy experts and former U.S. government officials sent a letter to President Barack Obama this week urging him to use U.S. air power immediately to patrol territory seized by the opposition. The mainly Republican group accused the president of "complicity in oppression" for failing to halt the bloodshed.
Associated Press writer Matthew Lee and AP Intelligence Writer Kimberly Dozier contributed to this report.