Syrian rebels, some carrying weapons supplied by the U.S., are making a new push for Damascus, in what marks a rare success for rebels against the regime of President Bashar Assad. The attacks on the capital and its surrounding suburbs are being led by a rebel faction that is a part of a larger group that has in recent months gained ground in the northern city of Aleppo and taken control of other rebels, some of whom have U.S. weapons. 

That group, Jaysh al-Islam, or "The army of Islam," has made enough advances recently that it may prove to be an attractive candidate for the position, currently vacant, of rebel group supported by Washington -- even though it's not a secular group, and may even harbor extremists.  

Forces loyal to Assad fought their “fiercest battle yet” during the weekend against Jaysh al-Islam in Douma, east of the capital, according to the Syrian Observatory for Human Rights. Jaysh al-Islam, also known as the Islamic Front, joined other rebel groups in December to form what is now known as the Levant Front, which has become the leading rebel group in the North. The newly merged group has taken control of bases previously held by Harakat Hazzm, one of the main benefactors of U.S. aid. But the Levant Front has also successfully fought an avowed American enemy: Jabhat al-Nusra, the local offshoot of al Qaeda, as well as other extremist factions around Aleppo.

The group is now switching its focus to the south, which may bring its effort within the U.S. strategy of supporting rebels based in the south of Syria. 

International Business Times reported in December the U.S. had stopped sending weapons to some rebel groups in the North because they were losing battles to Jabhat al-Nusra. Wary of more weapons falling into extremist hands, the U.S. began vetting new groups in the South. 

Rebels on the ground in Aleppo told IB Times the vetting process is still underway and the U.S. has yet to find a definitive group to support in the South. The constantly shifting alliances among rebel groups in Syria and the mix of extremists fighters in factions that are considered largely moderate, has complicated the vetting process. But if Jaysh al-Islam continues to advance around Damascus, the U.S. may have no choice but to send arms its way. 

In its advance, the group is facing pro-regime forces fighting under the umbrella of Jaysh al-Waffa, or "The Loyalists' Army," a faction formed three months ago to stave off rebels in Ghouta near Damascus.

Assad's air force supported the pro-regime forces fighting on the ground against the rebels. The Syrian Observatory for Human Rights said the regime has conducted more than 650 airstrikes across the country this month. And in the past two weeks Assad's military has increased its use of barrel bombs around the capital, killing dozens of civilians. Fifteen people were killed in Douma Monday. The recent violence in Damascus has brought the total death toll in the country to about 210,000 since the beginning of the war four years ago, the observatory said.