"At this point, Russia has been cooperative" in trying to get a cease fire deal in place between Syrian President Bashar al-Assad and the rebel forces looking to push him from power, he said.
Russian and Chinese delegations to the U.N. Security Council agreed to the plan drafted by U.S.-Arab League envoy Kofi Annan after weeks of intense negotiation.
The plan would call for Assad to pull his forces back from positions around rebel enclaves in Homs and elsewhere in the country. Critics of the plan claim the deal does not force Assad from power.
The council's approval comes less than a month after Russian Foreign Minister Sergei Lavrov said Moscow would not back any plan that included "ultimatums and artificial deadlines."
Assad had agreed to the peace plan proposed by Annan and backed by the U.N. Security Council, but the ceasefire that took effect last week has not appeared to have held. U.N. Secretary General Ban Ki-Moon said Thursday that Syria is not keeping the truce as reports of violence continue.
Admitting Russia's cooperation in the Syrian peace process is a significant step forward — the country could do more to sway Assad's forces to lay down their arms.
Russia "could have a much more significant impact on the Assad [regime]" if it chose to, he said.
In March, Russia sent three warships to the Syrian coast along with a cadre of Russian marines and special-operations forces to conduct "anti-terrorism" missions in the country.
Prior to that deployment, Russian military advisers had been embedded with Syrian military units to conduct bilateral training missions.
However, even if Moscow did exert its diplomatic and political will on its longtime ally in the Middle East, it would do little to bring peace to the region.
Sens. John McCain (R-Ariz.), Joe Lieberman (I-Conn.) and Lindsey Graham (R-S.C.) issued a joint statement Thursday that called on the Obama administration to recognize the failure of the peace plan and to strongly consider military action.
“The only way to stop Assad’s campaign of slaughter is for the United States to take tangible steps with our friends and allies to help the Syrian opposition change the military balance of power on the ground,” they wrote.
To that end, Chairman of the Joint Chiefs of Staff Gen. Martin Dempsey told House defense lawmakers that Assad's forces are now facing a "full-fledged insurgency."
But any potential military response "is best solved by regional actors with [U.S.] support," the four-star general added.
However, Panetta reiterated that even though the United States is keeping the military option on the table, the White House will keep pushing for a political solution to the crisis.