BEIRUT (AP) -- After five weeks of battle, Syrian government troops captured a strategic town near Damascus, cutting an arms route for rebels trying to topple President Bashar Assad's regime, state media and activists said Thursday.
By taking the town of Otaybah, east of the capital, the army dealt a major setback to opposition forces that in recent months have made gains near the city they eventually hope to storm.
Also Thursday, the White House and other top Obama administration officials said that U.S. intelligence has concluded with "varying degrees of confidence" that the Syrian government has twice used chemical weapons in the civil war, which has dragged on for two years.
However, officials also said more definitive proof was needed and the U.S. was not ready to escalate its involvement in Syria beyond non-lethal aid despite President Barack Obama's repeated public assertions that Syria's use of chemical weapons, or the transfer of its stockpiles to a terrorist group, would cross a "red line."
Syria's main Western-backed opposition promptly called on the international community to act "urgently and decisively." The opposition's statement said: "Failure to act will be seen by the regime as encouragement to use chemical weapons on a larger scale in the future."
Ahmad Ramadan, a member of the Syrian National Coalition opposition group's executive body, called the U.S. assertion an "important step" that should be followed by actual measures. "The U.S. has a moral duty to act ... we are waiting for the next steps," he told The Associated Press by phone from Istanbul.
The Syrian conflict began with largely peaceful protests against the Assad regime in March 2011, but eventually turned into a full-scale civil war. The fighting has exacted a huge toll on the country, killing an estimated 70,000 people and laying waste to cities, towns and villages.
With fresh supplies of weapons from foreign backers, the rebels have recently seized military bases and towns south of the capital in the strategically important region between Damascus and the border with Jordan, about 160 kilometers (100 miles) away.
The regime has largely kept the rebels at bay in Damascus, although opposition fighters control several suburbs of the capital from which they have threatened the heart of the city, the seat of Assad's power. Last month, government troops launched a campaign to repel the opposition's advances near the capital, deploying elite army units to the rebellious suburbs and pounding rebel positions with airstrikes.
The director of the Syrian Observatory for Human Rights, Rami Abdul-Rahman, said government troops regained control of Otaybah late Wednesday.
State-run SANA news agency said Thursday that the army has "restored complete control" over Otaybah. The official news services also said Assad's troops "discovered a number of tunnels which were used by terrorists to move and transfer weapons and ammunitions."
The regime and state media refer to rebels as terrorists and accuse them of being part of a foreign plot seeking to destroy Syria.
"It's a huge victory for the regime, and a big blow to the opposition that is now in danger of losing other towns and villages around Damascus," Abdul-Rahman said of the army's campaign.
On Thursday, the army was already capitalizing on the territorial gains, pounding southern suburbs of Damascus, including the long-contested Daraya with artillery barrages and airstrikes, according to the Observatory. The group, which relies on a network of activists on the ground, also reported fierce clashes between rebels and army troops to the east of the capital.
The army's offensive to dislodge rebel fighters from neighborhoods ringing Damascus is part of the government's broader campaign to secure central provinces of Hama and Homs, and areas along the Lebanese border. The region is of strategic value to Assad's regime because it links Damascus with the coastal enclave that is the heartland of Syria's Alawites and also home to the country's two main seaports, Latakia and Tartus.
Syria's regime is dominated by the president's minority Alawite sect -- an offshoot of Shiite Islam -- while the rebels are mostly from the country's Sunni majority. Assad's major allies, the Lebanese militant Hezbollah group and Iran, are both Shiite.
Otaybah is located on a road linking Damascus with the eastern suburbs of Damascus known as Eastern Ghouta. Rebels have been using the road to transport weapons and other supplies to the capital. Many of the capital's surrounding towns and neighborhoods have been opposition strongholds during the 2-year-old conflict.
Losing control of the town will make the defense of rebel enclaves in northeastern suburbs such as Douma, Harasta and others more difficult, Abdul-Rahman said.