By Kristina Wong - 01/29/16 10:50 PM EST
The Islamic State in Iraq and Syria (ISIS) has lost about 40 percent of the territory it once held in Iraq, but only about "five percent" of the territory it once held in Syria, Operation Inherent Resolve spokesman Col. Steve Warren said Friday.
While the number has been "40 percent" for Iraq since mid-December, the number has varied for Syria.A White House fact sheet dated Jan. 15 had the same figure for Iraq, but said ISIS had lost "more than 10 percent of the populated territory it once controlled in Syria."
And on Jan. 5, Warren told reporters in Baghdad that ISIS lost 40 percent of the territory it once held in Iraq but "20 percent" in Syria, according to Reuters.
"We believe in Iraq it's about 40 percent ... And Syria, harder to get a good number, we think it's around 20," Warren said.
The U.S. first began bombing ISIS in Iraq in August 2014, and in Syria in September 2014.
Meanwhile, Warren said Russian airstrikes in Syria have helped the Assad regime.
Russia began its airstrike campaign in September, to bolster Syrian President Bashar Assad in its civil war against U.S.-backed Syrian rebels and ISIS.
"The Russian airstrikes have made a difference for the regime. The Russian airstrikes have helped strengthen Bashar al-Assad, particularly in the Aleppo region, where Russian airstrikes have been probably most intense," Warren said.
Warren said Russian airstrikes have allowed Assad to push back both moderate Syrian rebels and ISIS in Aleppo.
The assessment comes as the United Nations began a round of political negotiations in Geneva to resolve the civil war in Syria.
The talks are "proximity talks," where opposition and regime representatives would not meet directly, but with other participants in separate rooms.
The main Syrian opposition group, the High Negotiations Committee (HNC), agreed to travel to Geneva, but said it wanted to discuss an end to Russian and regime airstrikes, sieges, and other humanitarian issues before engaging in negotiations.
Sen. John McCain (Ariz.), who spoke with the HNC's prime minister Friday, and Sen. Lindsey Graham (S.C.) called the group's demands reasonable and said they were disturbed by reports the U.S. had encouraged it to drop them.
"As these talks have been organized, the Assad regime has continued its assault on Syrian civilians backed by Russian air attacks, denied humanitarian aid to besieged areas, and unjustly and inhumanely detained innocent women and children," they said in a statement.
“We support the decision of the High Negotiations Commission to send a delegation to Geneva in order to advance a political solution in Syria, which will peacefully transition from the Assad regime to a democratic, pluralistic government which respects the dignity of all Syrians," they added.
"We understand that this difficult decision was made based on commitments from the U.S. government that a political transition will be discussed. We urge the Administration to uphold those commitments as well as prior commitments to the Syrian opposition that Assad can have no role in the future of Syria. If it does not, it would be understandable if the Syrian opposition chose not to participate further in these discussions.”