(CBS News) WASHINGTON - Amid warnings that the Syrian military appears to be "lining up" for a "massacre" in Aleppo - the war-torn nation's most populous city - the U.S. government says President Bashar Assad's isolated regime is literally running out of cash to keep up the fight.
Officials at the U.S. Treasury and State Departments tell CBS News that Syria is having problems finding a source to print its currency. That could make it harder for the regime to continue functioning as Assad's government burns through the state's central bank reserves.
Assad is estimated to have spent about half of Syria's sovereign wealth fund - essentially the nation's piggybank. It was estimated to be worth $5 billion just two years ago.
European Union sanctions - coordinated with the U.S. - have made it difficult for Syria to find new trading and banking partners. This is one of the financial tools that the U.S. is wielding.
Unilateral economic sanctions against Syria and 26 key members of the Assad regime were tightened again last week by the United States.
Still, sanctions are a blunt tool in a de facto financial war on Syria; the cost of living has skyrocketed not just for the Syrian regime, but also the Syrian civilians who support the opposition. Annual inflation is estimated to be up more than 30 percent.
The bottom line is that sanctions may not save any lives in Aleppo, which activists say is now surrounded by government tanks and had been strafed by fixed-wing aircraft earlier this week, ahead of the expected offensive.
But they are helping rebels in their fight against Assad.
U.S. officials believe Iran is now Assad's single remaining source for weapons. In a briefing at the State Department on Thursday, spokeswoman Victoria Nuland cited the presence of Qassem Suleimani, who directs a special unit of the Islamic Revolutionary Guard Corps, in Damascus last week as an overt sign of active Iranian support for the Syrian regime.
EU sanctions have made it expensive and difficult for Russia to continue supplying military equipment to Syria, according to the U.S. officials.
State Department officials say the various rebel groups on the ground have requested different types of support from the U.S., but claim that they have all consistently said that they do not want "boots on the ground."
Various sources within the State Department have voiced fear that "Americanizing" the war in Syria would ultimately be divisive within rebel forces, and perhaps feed sectarian violence.
There is also little political will within U.S. leadership for an intervention.
However, multiple U.S. policymakers - who remain anonymous as they are not authorized to speak on intelligence matters - acknowledge that the U.S. is not stopping other allied states from giving weapons to the rebels.
The U.S. officially provides no "lethal" assistance to the rebels, on the grounds that guns could be used in sectarian warfare retributions, particularly in the event the Assad regime falls. Even actionable intelligence that could help guide rebel attacks on government forces is considered "lethal," and thus off the table. Instead, the U.S. is distributing satellite phones and communications equipment to rebel forces so they can communicate and coordinate their own movements.
That leaves the financial tools as the main weapon being used against the Syrian regime.
The U.S. is helping civilians by providing food via the World Food Program and U.N. relief agencies.
And Washington is also helping the Syrian rebels plan for that "day after" Assad falls. Though policymakers won't share details of the planning for various "hard" and "crash landing" scenarios - such as a coup from within Assad's military, or the total implosion of the Syrian state after Assad falls - the U.S. does consistently point to the principles laid out by the opposition in documents like the National Compact (commonly referenced as the rebel "Bill of Rights" that resulted from meetings in Cairo earlier this month) as proof that the U.S. has confidence in the values of the potential new Free Syrian government.
This Compact lays out plans for managing the military, the economy and the shift in power to a temporary governing body that would draft a constitution and hold elections within a year.
The month of August will mark one year since the time that President Obama called for Assad to step down. History may ultimately decide the success of what appears to be the so-called "Obama doctrine," of hoping to maximize impact using a minimum of military support.
U.N. leader Ban Ki-moon issued an ominous warning to the international community on Thursday while visiting Srebenica, the site of a massacre in Bosnia during the 1990s. He said he doesn't want to see any of his successors visiting Syria 20 years down the road, and apologizing for "what we could have done now to protect civilians in Syria, which we are not doing."