Two leading senators on defense slammed the Obama administration for its lack of leadership in Syria after a weekend of extreme violence that saw any hope of a cease-fire crumble.

Sen. John McCain, R-Ariz., and Sen. Lindsey Graham, R-S.C., said the Obama administration must stop trying the same fix over and over again in Syria when both Russian President Vladimir Putin and Syrian President Bashar Assad have demonstrated that he "is not interested in diplomacy."

"How many hospitals, markets, schools and playgrounds do Russian and Syrian regime aircraft have to bomb before we realize that Putin and Assad are not interested in stopping the violence?" the two senators said in a statement. "Putin and Assad do not want to broker peace. They want to win a war. And American inaction is helping them to do it."

Russian and Syrian warplanes bombed Aleppo, Syria, over the weekend at an increased pace following the failed cease-fire, killing hundreds of civilians and decimating what structures remain in the war-torn city, including hospitals and medical facilities. Secretary of State John Kerry has released statements condemning the violence.

"After yet another cycle of this diplomatic masquerade, Russian and Syrian regime forces have unleashed new waves of airstrikes in Aleppo that no longer just indiscriminately target civilians, but now deliberately target humanitarian convoys, aid warehouses and rescue workers responding to the bloodshed," McCain and Graham said.

"But, as Assad and Putin lay the ground work to starve or butcher the 250,000 Syrians in eastern Aleppo, President Obama's policy remains shockingly unchanged."

Deputy Secretary of State Antony Blinken will be on Capitol Hill on Thursday to testify at the Senate Foreign Relations Committee about the state of affairs in Syria, following a two-day trip to Turkey to talk about the fight against the Islamic State.