Children run after what activists said was shelling by forces loyal to Syrian President Bashar al-Assad near the Syrian Arab Red Crescent center in the Douma neighborhood of Damascus on May 6, 2015. (Bassam Khabieh/Reuters)

Syrian President Bashar al-Assad acknowledged Wednesday that his forces have suffered a string of startling defeats in recent battles with reinvigorated rebels, who have made sweeping advances in the past few weeks.

In an unusual admission during a ceremony in Damascus commemorating Martyrs Day, Assad referred to recent rebel seizures of territory in the north and the south as “setbacks,” which he attributed to the “ups and downs” of war.

The usually upbeat leader painted a sober picture of the fighting, urging Syrians to “boost the morale of the soldier” and explaining the recent routs of his forces as “retreating when circumstances necessitate that.”

Some analysts see the gains by the opposition as a sign that Assad’s hold on power is weakening as the four-year-old conflict drags on. The fighting has killed about 220,000 people and displaced millions, producing one of the world’s worst humanitarian disasters in decades.

A new coalition of largely Islamist rebel groups, which includes Syria’s al-Qaeda affiliate, has inflicted heavy losses on government forces in key areas in the country’s northwest. In the south, a more moderate grouping of rebels is making inroads, threatening Assad’s hold on the city of Daraa, the capital of Daraa province, and advancing north toward Damascus.

The assaults appear to undermine Assad’s argument that his government forms a formidable bulwark against extremist groups such as the Islamic State, which has captured large chunks of eastern Syria as well as swaths of northern Iraq.

Still, in his address, the Syrian leader showed no sign of relenting in the fight against the rebellion. Assad also dismissed a recent flurry of speculation about cracks in his regime, blaming such talk on what he described as a coordinated campaign by opponents seeking to portray his government as weak.

He said politicians and journalists were “reemerging” from their holes to spread “propaganda” about his supposedly weakened authority. It was an apparent reference to speculation two years ago that the Syrian leader was on the verge of being ousted.

Analysts attribute the recent rebel advances to a rapprochement involving Saudi Arabia, Turkey and Qatar, which until recently had pursued independent and often contradictory policies in the Syrian conflict. Since taking the throne in January, however, Saudi Arabia’s King Salman has sought to repair rifts with the other countries with the goal of strengthening Syrian rebels, the analysts say.

The new Saudi regional strategy — which includes launching an air war against Shiite rebels in Yemen in March — is driven by a desire to challenge the regional influence of Iran, the Sunni kingdom’s foremost nemesis. Shiite-led Iran is a crucial backer of the Assad regime, providing military support and billions of dollars in aid to prop up the Syrian military and economy.

On Thursday, Adib Mayaleh, the governor of Syria’s central bank, told Bloomberg News that Iran had given preliminary approval for a $1 billion line of credit to the Syrian government.

Whether Iran can continue pumping cash and military support to Assad is uncertain, however. Tehran is weighed down by international sanctions and a costly war effort in Iraq, where Iranian forces are helping to battle Islamic State militants.

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