World powers have agreed to seek a nationwide "cessation of hostilities" in Syria to begin in a week's time, after talks in Germany. The halt will not apply to the battle against jihadist groups Islamic State (IS) and al-Nusra Front.
Ministers from the International Syria Support Group also agreed to accelerate and expand aid deliveries. The announcement comes as the Syrian army, backed by Russian air strikes, advances in Aleppo province. The move threatens to encircle tens of thousands of civilians in rebel-held parts of the major city of Aleppo.
"What we have here are words on paper, what we need to see in the next few days are actions on the ground," he said.
A task force chaired by the US and Russia will work to implement the truce through consultations with Syria's warring factions. Aid deliveries for besieged Syrian communities are due to begin as early as Friday.
Mr Kerry made the announcement alongside his Russian counterpart Sergei Lavrov and the UN special envoy for Syria, Staffan de Mistura. Mr Lavrov said there were "reasons to hope we have done a great job today". An earlier proposal from Russia envisaged a truce starting on March 1st.At the press conference Mr Kerry again suggested that Russian strikes were targeting what the West sees as moderate opposition forces, rather than terrorists, as Moscow says. British Foreign Secretary Philip Hammond said the cessation would only work if Russia halted its raids, although Mr Lavrov said they would continue.
Of course Russia will continue with it's campaign of airstrikes. In my opinion, they want the Sunni rebels and Kurds to surrender, to completely concede defeat and knuckle under to Assad's rule. That is the only condition under which hostilities will cease. Then they will focus on Islamic State incursions.
The Support Group also agreed that peace talks involving the Syrian government and rebels should resume as soon as possible. Initial talks were suspended just days after they began earlier this month in Geneva, in the wake of the Aleppo offensive.
Thousands of people displaced by the fighting have been stranded at the border with Turkey and aid agencies have warned of a rapidly deteriorating humanitarian situation.
A spokesman for the Syrian opposition, Salem al-Meslet, stated, "if we see action and implementation on the ground, we will be soon in Geneva". The rebels do not believe the agreement is worth the paper it's written on. They don't trust Assad or Russia to stick to any agreed terms. The Aleppo Offensive, launched by the Syrian army and backed by Iran and Russia continued, unabated, while peace talks straggled to a halt during the last attempt at a truce.
Syria conflict - key questions
Why is there a war in Syria?
Anti-government protests developed into a civil war that, four years later, has ground to a stalemate, with the Assad government, Islamic State, an array of Syrian rebels and Kurdish fighters all holding territory.
Who is fighting whom?
Government forces concentrated in Damascus and the centre and west of Syria are fighting the jihadists of Islamic State and al-Nusra Front, as well as less numerous so-called "moderate" rebel groups, who are strongest in the north and east. These groups are also battling each other.
How has the world reacted?
Iran, Russia and Lebanon's Hezbollah movement are propping up the Alawite-led Assad government, while Turkey, Saudi Arabia and Qatar back the more moderate Sunni-dominated opposition, along with the US, UK and France. Hezbollah and Iran are believed to have troops and officers on the ground, while a Western-led coalition and Russia are carrying out air strikes.