A year into the uprising in Syria, senior U.S. intelligence officials described the nation’s president, Bashar al-Assad, on Friday as firmly in control and increasingly willing to unleash one of the region’s most potent militaries on badly overmatched opposition groups.

The officials also said Assad’s inner circle is “remaining steadfast,” with little indication that senior figures in the regime are inclined to peel off, despite efforts by the Obama administration and its allies to use sanctions and other measures to create a wave of defections that would undermine Assad.

Assad “is very much in charge,” said a senior U.S. intelligence official responsible for tracking the conflict, adding that Assad and his inner circle seem convinced that the rebellion is being driven by external foes and that they are equipped to withstand all but a large-scale military intervention.

“That leadership is going to fight very hard,” the official said. Over the long term, “the odds are against them,” he said, “but they are going to fight very hard.”

The comments, provided by three intelligence officials on the condition of anonymity to share candid assessments, were the most detailed to date by U.S. analysts on the status of the uprising, which began last March.

The officials said the regime’s tactics have taken a more aggressive turn, and newly declassified satellite images released Friday show what officials described as “indiscriminate” artillery damage to schools, mosques and other facilities in the beleaguered city of Homs in recent weeks.

Overall, they described Syria as a formidable military power, with 330,000 active-duty soldiers, surveillance drones supplied by Iran and a dense network of air defense installations that would make it difficult for the United States or other powers to establish a no-fly zone.

“This is an army that was built for a land war with the Israelis,” said a second senior U.S. intelligence official. After the regime hesitated to attack civilian population centers earlier in the conflict, its “restraint . . . has been lifted,” the official said.

Diplomatic visits

Syrian forces continued their month-long shelling of the opposition stronghold of Homs, in the west-central part of the country, on Friday, according to news reports. Thousands demonstrated in other parts of the country ahead of a visit by Kofi Annan, the special envoy of the United Nations and Arab League. Annan, who arrived in Damascus on Saturday, met with Assad later in the day to press for a political solution to the crisis.

U.N. humanitarian chief Valerie Amos, who visited Homs this week, said she was “devastated” by what she saw in the ravaged city. “There are no people left,” she said.

Amos, speaking in Turkey after visiting refugee camps along the Syrian border, said the Assad government had agreed to a “limited assessment” of humanitarian needs but had refused “unhindered” access for aid organizations and “asked for more time” to consider U.N. proposals for extended assistance for civilians.

In Washington, the intelligence officials cited a number of factors protecting the regime from collapse. Not least among them is the level of motivation in an inner circle convinced that yielding power will mean death or life imprisonment.

U.S. intelligence has also detected an escalation in lethal support from Syria’s closest ally, Iran. Officials said that Iran had previously been supplying mainly training and equipment to suppress opposition forces but has recently begun sending small arms and sophisticated equipment for monitoring and penetrating rebel groups.

Iran has shared equipment and expertise developed during its efforts to put down its own internal rebellion in 2009. Syria also has a small fleet of unarmed drones that appear to have been supplied by Iran before the uprising began, the officials said.

They portrayed the political opposition to Assad as disorganized and hobbled by a lack of experienced leadership. The officials described efforts to unify and attract a broader following among Syria’s minority groups — another objective of U.S. policy — as having limited success. The Syrian National Council, dominated by exiles who are mainly Sunni Muslims, has been trying to attract Christians, Druze and Kurds away from Assad.

Fears that the opposition will oppress minorities or worse have been regularly stoked by the regime, which is dominated by Alawites, an offshoot of Shiite Islam.

Opposition forces

The intelligence officials also echoed concerns expressed by U.S. military leaders in congressional testimony this week about providing weapons to the armed elements of the opposition. They are equipped mainly with small arms and rocket-propelled grenades, giving them little firepower compared with Assad’s formidable forces.

An estimated 10,000 to 20,000 soldiers have defected and form the bulk of the Free Syrian Army. It is organized loosely, without effective command and control, and it has few links to the political opposition, according to U.S. intelligence accounts.

Protecting those forces would be a daunting task. One of the officials said that Syria’s air defenses include hundreds of surface-to-air missile sites and thousands of antiaircraft artillery installations.

Describing the dimensions of the challenge, this official said that Syria, barely one-tenth the size of Libya, has an army four times as big with five times the air defense assets, most of it supplied by Russia.

So far, the officials said, the bloodiest attacks against the regime appear to have been carried out by al-Qaeda elements seeking to slip unannounced into opposition groups that do not seem eager to have any affiliation with the terrorist network.

The U.S. officials said that al-Qaeda’s affiliate in Iraq has reversed the flow of a pipeline that once carried fighters and weapons through Syria to battle U.S. forces at the height of the Iraq war.

“That network is still there,” said the first U.S. intelligence official, who acknowledged that the size and composition of the al-Qaeda presence in Syria is unclear. Some al-Qaeda members may be Syrian, others Iraqis.

The officials said their judgment that AQI — as the Iraq affiliate is known — was behind vehicle bombings that killed dozens of people in Damascus and Aleppo in December and January is based more on the nature of the attacks than independent evidence of al-Qaeda involvement.

The greatest damage done so far to Assad’s regime has been economic, intelligence officials said. Sanctions imposed by the United States and the Arab League, as well as European curbs on importation of oil, have caused spikes in unemployment, fuel prices and budget deficits in Damascus.

Over the long term, the officials said, economic hardships may be the most effective tool for unseating Assad. Still, the first U.S. intelligence official said, “to this point, we have not seen that having an effect on the regime’s ability to prosecute the war.”