US Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov announced the agreement after three days of talks in Geneva.
They said they would seek a UN Security Council resolution that could authorise sanctions - short of military action - if President Bashar al-Assad's government fails to comply.
Under the pact, Syria must begin by submitting a "comprehensive listing" of its chemical weapons stockpiles within one week, said Kerry.
In Washington, President Barack Obama said he was willing to give diplomacy a chance but warned the military option was still on the table.
"We are not just going to take Russia and Assad's word for it. We need to see concrete actions to demonstrate that Assad is serious about giving up his chemical weapons," Obama said in his weekly address on Saturday.
The deal announced by the diplomats includes what Kerry called "a shared assessment" of Syria's weapons stockpile, and a timetable and measures for Syria to comply.
It calls for international inspectors to be "on the ground in Syria by November" and to complete their initial work by the end of that that month.
All of Syria's chemical weapons stocks, material and equipment would have to be destroyed or removed by mid-2014.
But the stakes have been especially high in Geneva, because the negotiations between the United States and Russia on securing Syria's chemical weapons also are considered key to breaking the international stalemate that has so far blocked a resumption of peace talks to end the Syrian civil war, now in its third year.
"We have committed to a standard that says, verify and verify," Kerry told a news conference in the InterContinental Hotel in Geneva, where he has been staying and the negotiations were conducted since Thursday night.
Among the highlights of the agreement is that the US and Russia would agree to work together on a new, binding Security Council resolution that would ensure verification of the agreement to secure and destroy Syria's chemical weapons stocks and remove its capability to produce such weapons.
The resolution would allow for punitive measures for non-compliance, but stop short of military action, if the 16-nation Security Council approves them.
The US and Russia are two of the five permanent Security Council members with a veto. The others are Britain, China, and France.
Another major feature of the agreement is that the US and Russia plan to give Syria one week, until Sept 21, to submit "a comprehensive listing, including names, types and quantities of its chemical weapons agents, types of munitions, and local and form of storage, production, and research and development facilities".
In addition, the US and Russia have agreed that international inspectors should be on the ground in Syria by November and complete their initial work by the end of the month. They must be given "immediate and unfettered" access to inspect all sites.
Notably, Kerry said they had agreed on grounds under which they might request a Security Council "Chapter 7" resolution at the UN, which is a measure that could include military and non-military sanctions.
But Lavrov, who said the agreement was "based on consensus and compromise and professionalism", indicated there would be limits to using a Chapter 7 resolution, which Russia would almost certainly veto if it specifically authorised a military strike such as what Obama has threatened.
"Nothing is said about the use of force or about any automatic sanctions. All [responses to] violations should be approved by the Security Council," Lavrov said.
Kerry said the two countries' teams of experts had come to agreement on the exact size of Syria's weapons stockpile, which had been a sticking point before their meetings in Geneva.
The agreement over the Russian proposal to inventory, isolate and eventually destroy Syria's chemical weapons stocks comes as the Obama administration warned that there is a timetable for a diplomatic resolution of the weapons issue.
Obama underlined his stand in his weekly radio address on Saturday by saying: "Since this plan [to give up chemical weapons] emerged only with a credible threat of US military action, we will maintain our military posture in the region to keep the pressure on the Assad regime."