MUNICH — Secretary of State John Kerry and his Russian counterpart, Sergey V. Lavrov, announced that they had agreed on the delivery over the next few days of desperately needed aid to besieged Syrian cities, to be followed by a "cessation of hostilities" within a week on the way to a more formal cease-fire.
"We have agreed to implement a nationwide cessation of hostilities in one week's time," Kerry said early Friday, after all-day meetings. "That is ambitious."
"The real test is whether all the parties honor those commitments," he said, sitting next to Lavrov, the two men doing their best to appear cooperative after weeks of trading accusations over the accelerated Russian air campaign that has given new support to the government of Syria's president, Bashar Assad.
If executed, the agreement, forged by the International Syria Support Group, would mark the first sustained and formally declared halt to fighting in Syria since the civil war began in 2011, early in the Arab uprisings. But even a formal cease-fire would be partial — it excludes the Islamic State, also known as ISIS or ISIL, and the Nusra Front, both designated as terrorist organizations by the United Nations — and highly fragile.
At moments during a nearly hourlong news conference Kerry and Lavrov used the phrase "cessation of hostilities" and "cease-fire" interchangeably. But Kerry acknowledged the first was more temporary, and "a cease-fire is more permanent," a recognized series of steps in international law.
What he envisions a week from now, Kerry said, "is a pause." But the practical effect should be "ending hostile activity" while food is airdropped and driven into war-torn areas. Most are held by the government, some by rebel groups.
There are many reasons to question whether either the relief effort or a meaningful cease-fire will come to pass, or achieve the goal of ending the conflict.
But the announcement early Friday in Munich marked the first time there was hope of a break in the violence since the civil war began in 2011. And it would be the first large-scale aid to the country, from where 4.4 million have fled and millions more are internally displaced.
In the daylong meetings, all the major players seemed to recognize that Syria had reached a breaking point. Yet neither Kerry nor Lavrov could say whether leaders of all the fractious rebel groups have agreed to go along, or how Assad's government would comply. And it is clear that the two nations still have a sharp difference of opinion over which groups constitute "terrorists"; the Russians have been bombing some rebel groups that the United States has been supplying, arguing that they are linked to the Nusra Front or other terrorist organizations.
There is no evidence that difference has been resolved.
Timing is critical for all sides. Russia proposed this week starting a cease-fire in early March. Some U.S. officials say privately they are concerned that Russia would use the time to help Assad's forces, aided by the Iranian military, to seize more territory.
Even if they did not, any formal cease-fire could essentially freeze in place the recent battlefield gains Assad's forces have made with the help of Russian airstrikes. In the city of Aleppo, divided for four years between government and insurgent forces, the rebel-held Eastern section has been bombed by Russian aircraft as government troops attempt to encircle it.
Kerry bristled at the suggestion that by agreeing to the cessation of hostilities in the next week now he was acceding to Assad's recent territorial gains, or setting the stage for Assad to create a rump Syrian state comprised major population centers.
"Yes, I agree the bombing the of past few weeks has made a difference for Assad," he said. "But that difference does not end the war." The more territory Assad seizes, Kerry said, "the more successful he is in creating terrorists."
Both the aid and the cessation of hostilities will be monitored by task forces, the two men said. Kerry said he and Lavrov would chair the task force monitoring cease-fire activities, and receive reports of violations. An earlier Russian proposal contained no verification measures.
Lavrov, for his part, was defensive about accusations from human rights groups that Russian bombs have been hitting civilian targets, sending tens of thousands of people fleeing across the border in recent days. "Some do lie," he said of the groups. He suggested some news organizations were bending the facts as well, but he did not name them.
He also said the agreement announced early Friday called for more military cooperation between the Russian and U.S. military, something the United States has resisted. But he did not elaborate on what form that cooperation would take.
Earlier Thursday, Defense Secretary Ash Carter met with defense ministers of the countries taking part in the campaign against the Islamic State group. All but a few of the 40 countries in the coalition have "stepped up to do more in the last months and days," he said.
Carter said 90 percent of the countries had made pledges, but he did not offer many specifics on what the contributions would be. It also remained unclear what effect any new assistance would have on the battlefield, or even how many leaders would be able to deliver on their commitments.
"There's just a great deal going on," Carter said at a news conference after the meeting. He added that he was "happy to see so much going on" but that "we're also impatient."
Carter said that by the time leaders met next month in the United States to discuss the campaign, "We should begin to see tangible gains from the additional capabilities the coalition is bringing to bear against ISIL."
When asked what those gains might be, he said that there were some expectations and details he could not discuss.