WASHINGTON — As members of the Senate blasted the Obama administration's strategy in Syria and Iraq Tuesday, new data shows that the frequency of US airstrikes on Islamic State targets in Syria has slowed significantly since Russia began military operations in the region in early September.

US strikes on Islamic State militants in Syria averaged about seven per day in August, a pace similar to the entire first year of the air campaign that began last year, DoD data shows.

But in September, after the Russians began setting up a military base at Syria's Latakia airport, the pace of American airstrikes in Syria fell to an average of slightly more than four per day.

And from Oct. 1 through Oct. 26, as the Russians began airstrikes on targets in Syria supporting embattled President Bashar al-Assad, the daily average of airstrikes fell even further to below four per day, the data shows.

Military officials say the drop in airstrikes is not related to the Russian military activity in the area.

"The Russian intervention has not significantly altered the Coalition's targeting in Syria," according to a statement from the Combined Joint Task Force Operation Inherent Resolve on Monday.

"We strike targets where we find them and vet them and in the order we want to attack them. So there may be ebbs and flows in the airstrike numbers," according to the statement provided in response to an inquiry from Military Times.

Daily U.S. airstrikes in Syria from Aug. 1 through late October.

Photo Credit: John Harman/Staff

That explanation is unlikely to mollify members of Congress who have become increasingly critical of with the Obama administration's strategy to fight the Islamic State, better known as ISIL or ISIS, since Russian intervention began.

Appearing in front of the Senate Armed Services Committee Tuesday, Secretary of Defense Ash Carter and Gen. Joe Dunford, chairman of the Joint Chiefs of Staff, faced accusations that the US had essentially ceded control of the situation in Syria to the government of Russian President Vladimir Putin.

Particularly aggrieved was Sen. Lindsey Graham, R-S.C., who accused Secretary of State John Kerry of "turning over Syria to the Russians and to the Iranians" before calling the US plan a "half-assed strategy at best."

Graham, currently polling poorly in the race for the GOP presidential nomination, pressed Dunford about whether there is any "credible military threat" to the Assad regime with Russia and Iran now backing it, to which Dunford replied, "I think the balance of forces right now are in Assad's advantage."

"Not his advantage. He is secure as the day is long," Graham said, animatedly.

Democratic Sen. Joe Manchin of West Virginia, meanwhile, indicated that in his mind,"Russia and Iran will have more influence on who the next leader or the leadership of Syria is going to be than we will."

Committee Chairman Sen. John McCain, R-Ariz, went after Carter for making the argument that Russian planes have not been striking Pentagon trained rebels in Syria. While a true statement, Carter's argument addresses only the small group of DoD-trained fighters and not the larger group of coalition trained and equipped groups that have received backing from other parts of the US government,

"You are making a distinction without a difference, Mr. secretary," McCain said angrily. "These are American-supported and coalition-supported men who are going in and being slaughtered."

While some Russian strikes have hit ISIL targets, the US contends the majority of strikes have come at the expense of groups fighting the Assad regime.

Carter was also forced to defend a loose agreement reached between Russia and the US-led coalition about safety procedures in case coalition and Russian jets encounter each other above Syria.

"To be clear, we are not cooperating with Russia and we're not letting Russia impact the pace or scope of our campaign against ISIL in Iraq and Syria. ... We will keep prosecuting our counter ISIL campaign unabated. We will keep supporting the moderate Syrian opposition, along with our other commitments to friends and allies in the region," Carter said.

On Oct. 20, the US and Russia forged a "memorandum of understanding" that outlined a series of safety procedures to prevent mishaps or misunderstandings.

Since the agreement was signed, US and coalition airstrikes in Syria have slowed further. There was only one strike between Oct. 22 and Oct. 25, a lull not seen for months.

A Pentagon official said the unusually slow pace of air strikes was unrelated to the agreement with the Russians.

"We simply haven't had any [strikes] that we've done in the past few days. It doesn't mean we're not on the lookout for them," Navy Capt. Jeff Davis, a Defense Department spokesman, said Monday.