GENEVA, Sept. 10 (Xinhua) — U.S. Secretary of State John Kerry and Russian Foreign Minister Sergey Lavrov announced on Saturday a landmark agreement on a nationwide cease-fire in Syria, which they hope would lead to their countries' military cooperation to end more than five years of bloodshed there.

Kerry, who spoke first during an early morning press conference Saturday here, said the plan aims to enable a nation-wide cessation of hostilities in Syria beginning Sept.12, allowing life-saving humanitarian aid to reach civilians in need.

"If the plan is implemented in good faith... this can be a moment where the multilateral efforts at the diplomatic table could take hold and provide the people of Syria with a transition,"  Kerry said after more than 13 hours of talks at a lakeside Geneva hotel.

His Russian counterpart welcomed the consensus while saying much work needs to be done to see the package take full effect.

"Today we have developed a significant, practical and concrete package of documents,"  he said, adding that  "this is not the end of the road, it is just the beginning of our new relations."

The first step of the plan is to reinstall a nation-wide cease-fire in the Middle East country for a minimum of seven days beginning at sundown Sept. 12, enabling humanitarian aid to reach civilians trapped in besieged and hard-to-reach areas, including the northern city of Aleppo.

The week-long truce is expected to pave the way for greater military cooperation between Washington and Moscow, including working on strategies targeting terrorist factions operating on Syrian soil.

Another crucial element of the package, which Lavrov says Syrian President Bashar al-Assad has given the green light to, is for Syria' s air force to end strikes against opposition strongholds.

"I want to emphasize, this step is absolutely essential, it is a bedrock of this agreement,"  Kerry said.

This is part of a broader long-term strategy to prevent Syrian warplanes from operating in areas singled out by the United States and Russia.

Opposition rebels fighting Syrian government troops alongside terrorist groups such as Nusra will also have to separate, a move greatly welcomed by Lavrov, who said this is included in the agreed-upon document.

The agreement is the culmination of much diplomacy and intense talks between both Kerry and Lavrov, who haven' t always seen eye to eye on the Syrian issue.

While Moscow backs al-Assad, Washington supports opposition groups seeking to oust him.

This is the first time both countries reach an agreement on such a comprehensive package. The breakthrough is seen by both officials has having the potential to provide a turning point for Syria, where the conflict has killed up to 500,000 people.

UN Special Envoy for Syria Staffan de Mistura welcomed the development, saying "the United Nations hopes that the implementation of this understanding will facilitate renewed efforts to reach a Syrian-owned and Syrian-led political settlement of the conflict as called for in the Geneva Communique and Security Council resolution 2254."