Searching for any sign of splintering in Syria’s ruling class, the United States has tracked what it suspects is the transfer of millions of dollars in foreign accounts by elites with ties to President Bashar al-Assad.

But the flow of money is murky. U.S. intelligence officials said they cannot estimate the total amount and are still trying to assess what the transfers mean: Is Assad’s inner circle starting to fray, or are wealthy Syrians simply hedging their bets?

The struggle to make sense of the money transfers underscores the degree to which many aspects of the uprising in Syria remain opaque to outside observers — including U.S. spy agencies — a year after internal efforts to oust Assad began.

Intelligence on Assad’s regime and its intentions has been fragmentary or out of focus, senior U.S. officials said. The composition and capabilities of Syrian opposition forces remain unclear. And U.S. analysts have been unable to reach firm conclusions on key questions, including whether al-Qaeda was responsible for a series of bombings in Syria in recent months.

Reliable intelligence on Syria “comes and goes,” said Rep. Mike Rogers (R-Mich.), chairman of the House intelligence committee. “It’s a mixed bag in Syria and probably rates on the low-acuity side.”

That has complicated policy issues for the Obama administration as it decides whether to arm or otherwise support Assad’s opponents.

Top U.S. defense officials said Wednesday that President Obama has authorized, and the Pentagon has completed, initial U.S. planning for possible intervention in Syria but that a lack of unity within the Syrian opposition and the international community argues against such a mission.

“There are no simple answers,” Defense Secretary Leon E. Panetta said at a contentious Senate Armed Services Committee hearing on Syria. “The result is a great deal of anger and frustration that we all share.”

In addition to tracking money transfers, U.S. spy agencies have scoured satellite imagery and signals intercepts to compensate for a shortage of “human intelligence” from inside a country long considered a key crossroads in espionage.

For the CIA, already stretched by the demands of two war zones and the domino-like toppling of Arab governments, Syria poses greater difficulties than other countries swept up in the Arab Spring.

In Libya, for example, the CIA was able to insert covert collection teams within weeks of the start of the conflict to make contact with rebel groups and gather intelligence firsthand.

In Syria, where outgunned opposition elements have struggled to claim and hold territory, the CIA has been forced to rely on a network of sources concentrated in Damascus and assistance from the intelligence services of Arab allies.

Asked which partners are providing the most help, a former high-ranking CIA official said, “anybody who’s Sunni” and, therefore, likely to oppose the Shiite Assad regime. The former official pointed to Saudi Arabia, Turkey and Jordan in particular.

The challenge for the CIA increased when the United States shut its embassy in Damascus last month. The facility had provided diplomatic cover for agency officers and a base for intelligence-gathering operations inside Syria’s capital.

Obama has refrained from issuing a classified “finding” that would give the CIA authority to conduct covert operations inside Syria against Assad, U.S. officials said.

Even in its core mission of gathering intelligence, the agency has been cautious, according to officials who described Syria as a sophisticated counterintelligence adversary, with substantial assistance from Iran.

No agency teams were sent to meet with opposition elements in Homs before that city became the target of a violent crackdown by Assad’s forces. And officials said no surveillance drones have been deployed over Syria, whose air defenses are considered more than capable of shooting down unmanned aircraft.

Instead, the U.S. agencies have had to monitor events — as well as Syria’s chemical weapons stocks — from higher altitudes.

The U.S. ambassador to Syria, Robert Ford, now based at the State Department in Washington, this week posted what he described as “declassified” American satellite images on a U.S. Embassy Facebook page to call attention to the “disproportionate nature of the Assad regime’s violence against the people and his willingness to attack civilian targets.”

The images show artillery units on the outskirts of Homs and depict heavy damage to facilities, including a mosque and medical clinic in the neighborhood of Bab Amr.

On Wednesday, the United Nations’ top humanitarian official became the first international observer to enter the ravaged neighborhood since a four-week siege ended last week.

Valerie Amos, the U.N. undersecretary general for humanitarian affairs, joined a team from the Syrian Arab Red Crescent. But the International Committee of the Red Cross continued to be denied permission to visit the neighborhood, the agency said in a statement from Geneva.

The Red Crescent team found that “the vast majority of residents had left their homes in recent days to seek refuge in neighboring areas,” according to the statement.

Despite ongoing violence — and American lawmakers’ growing frustration over perceived U.S. inaction — Pentagon officials said any military intervention would be exceedingly complicated.

“It would take an extended period of time and a great number of aircraft,” Gen. Martin Dempsey, chairman of the Joint Chiefs of Staff, told lawmakers Wednesday. Because most Syrian air defenses are in the heavily populated western part of the country, where most of the violence against opposition strongholds is occurring, civilian casualties and other collateral damage would be high, he said.

Assessments from top U.S. intelligence officials on the main question of whether Assad is likely to remain in power have shifted, sometimes in a span of weeks. After previously predicting that it was only a matter of time before Assad fell, Director of National Intelligence James R. Clapper Jr. testified last month that Assad seemed poised to hold power indefinitely.

In that same Feb. 16 hearing, Clapper cited “signs of some of the seniors in the Assad regime making contingency plans to evacuate, move families, move financial resources,” before adding that “to this point they’ve held together.”

The question of whether Assad’s inner circle could disintegrate is critical for the United States and the Arab League, which have imposed economic sanctions on the country as well as more than a dozen senior members of Assad’s government to turn them against the regime.

To protect his rule, Assad has relied on brutal repression of adversaries as well as economic policies that have enriched relatives and members of the Alawite religious sect at the core of the regime.

“That’s the real mortar that holds the regime together,” said Andrew Tabler, a Syria expert at the Washington Institute for Near East Policy. “Those people make millions of dollars a year. They’re heavily invested in the system. The problem is we don’t have a very good sense of the [relationships] among them and at what point they would break.”

U.S. officials said the money transfers, which probably involve accounts in such countries as Dubai and Lebanon, are seen as potential flares of trouble for Assad. But analysts at the Treasury Department and other agencies have only shards of information on the flows and little ability to discern what they mean.

“The sense that we get is it’s precautionary,” Rogers said. “I think this is all people covering their bets.”

Staff writers Liz Sly in Beirut and Karen DeYoung in Washington contributed to this report.