WASHINGTON - Influential Republican Senator John McCain said on Tuesday he is working to modify a congressional resolution authorizing US military force in Syria to include a "strict" timeline for Syria to turn over chemical weapons.The amendment is a response to new diplomatic developments designed to ward off a US military strike, highlighted by Russia's agreement Monday to get Syria to turn over its chemical weapons.Speaking on CBS' "This Morning" program, McCain said he was "extremely skeptical" about such a diplomatic solution but that "to not pursue this option would be a mistake." "Some of us are already working on a modification to a Congressional resolution that would require strict timelines and strict guidelines that would have to be met as part of the authorization for the president" to use military force, he said.McCain offered few specifics about his measure, but other lawmakers have also been floating proposals that would allow a certain window of time before allowing President Barack Obama to take further action, which could include air strikes.Crisis in Syria - full JPost.com coverageDemocratic Senators Joe Manchin and Heidi Heitkamp are pushing an alternative that gives the Assad government 45 days to sign an international chemical weapons ban and begin the process of turning over its weapons.The shift among some lawmakers comes amid a dramatic turnabout in the response toward Syria following last month's chemical weapons attack against civilians, which Washington blames on Syrian President Bashar Assad's government. Washington says the Aug. 21 attack near Damascus killed more than 1,400 people and Obama has been pressing Congress to grant him authority to take action against Syria in response.Syria said on Tuesday it had accepted the Russian proposal for it to give up its chemical weapons, winning it a possible reprieve from US strikes even as its warplanes bombed rebel positions in Damascus.McCain, on CNN's "New Day" program, said his proposed changes could be offered as an amendment and would require "guidelines, reporting process and benchmarks that have to be met."International monitors should immediately be sent to Syria's chemical weapons sites and secure Assad's cache immediately while the international community works out a deal for their control and disposal, McCain said."If he's serious, then let the monitors in there right away. We know where these chemical weapons sites are, and get them under control immediately," McCain told CBS.Last week, a US Senate panel narrowly passed a resolution authorizing limited military action. This had been expected to come up for a vote in the full Senate this week, but with opposition building from lawmakers from both parties, Senate Majority Leader Harry Reid put off a vote.