Secretary of State John F. Kerry and Russian Foreign Minister Sergei Lavrov meet in Geneva on Friday. (Martial Trezzini/AP)

The United States and Russia failed Friday to reach a final agreement on a U.S.-proposed deal to coordinate their air attacks on terrorist groups in Syria and to stop Russian and Syrian bombing of civilian and rebel-held areas, but said they were close and would continue discussions.

“We’re not going to rush to an agreement until it satisfies fully the needs of the Syrian people and the ability of the international community to address them,” Secretary of State John F. Kerry said after more than nine hours of talks here with Russian Foreign Minister Sergei Lavrov.

“We made a number of steps forward,” Lavrov said in a late-night news conference with Kerry. “The fact that we’re not making them public does not mean that we are not getting closer.”

Both noted a reluctance to repeat past experiences during the five-year civil war, when agreements fell apart, at times even before they had begun to be implemented.

“I don’t want to make an announcement, nor does President Obama want to make an announcement, that is not enforceable, that does not have details in place, that winds up in the same place as the last two announcements,” Kerry said.

Aid ambulances line up in Darayya, a blockaded Damascus suburb. Rebels agreed to evacuate after four years of grueling bombardment and a crippling siege. (AP)

Neither he nor Lavrov provided details on progress toward resolving what appeared to be the broad remaining chasm between them: how to stop Syrian government and Russian bombing of civilians, and how to persuade U.S.-backed opposition forces to separate from the terrorist groups many of them are fighting beside.

“To have details that still need to be worked out after 10 hours of negotiations and basically the same meeting a month ago — this indicates political, not technical, decisions are required by Obama and [Russian President Vladimir] Putin,” said Andrew Tabler of the Washington Institute for Near East Policy.

Kerry and Lavrov said their “technical teams” will continue to talk, and Kerry indicated that an agreement, if it is possible, could be reached within the next week. The overall goal is to reinstate a cease-fire that was partially successful for several weeks late last winter and to relaunch political talks that fell apart along with the truce.

Since then, however, the situation on the ground has gotten worse rather than better, with steadily increasing air bombarment by Syria and Russia, and growing overlap between U.S.-backed opposition forces and at least one of the two terrorist groups both the United States and Russia consider legitimate targets: the Front for the Conquest of Syria — or Jabhat Fatah al-Sham, the al-Qaeda affiliate formerly known as Jabhat al-Nusra — and the Islamic State.

Much of that fighting has taken place in the northern city of Aleppo, where the Front and opposition rebels, as well as the government, have blocked access routes to humanitarian aid for more than 1 million civilians stranded under brutal air and ground fire. No resolution to the Aleppo situation was announced after the meeting.

Kerry first made the truce and coordination proposal during a visit to Moscow last month. Since then, the carnage in Syria has only increased, with Aleppo becoming a humanitarian disaster zone and aid still blocked to nearly two dozen similarly besieged towns and cities.

A child waves at Turkish troops heading to the Syrian border. (Halit Onur Sandal/AP)

A U.S.-Russian military and intelligence working group agreed over the past several weeks on maps demarcating the primary locations of the Islamic State and the Front, places where those groups are mixed with U.S.-backed rebel fighters, and areas primarily populated by civilians. The Front for the Conquest of Syria formally split from al-Qaeda last month and changed its name from Jabhat al-Nusra.

Under the proposal, the Syrian government would cease combat air operations, the rebels would stop firing at government positions, and only the two terrorist groups — the Islamic State and the Front — would be targeted by coordinated U.S. and Russian airstrikes.

Russia has said it cannot agree until the United States and its coalition partners are able to sufficiently separate the rebel groups they back from the terrorist fighters in areas where they overlap. With the escalation of fighting in Aleppo, those groups have become more intertwined.

For its part, the United States has said Russia and the Syrian air force have used the overlap as a smokescreen to continue their attacks on rebel groups fighting to oust President Bashar al-Assad.

U.S. refusal to become a direct participant in the civil war, even as it escalates its air attacks against the Islamic State and says it will target the Front, has become increasingly difficult to maintain on the ground as the once-separate battlefields have edged closer together and multiple forces are fighting with different agendas.

This week, Turkey entered the fray, sending tanks, troops and aircraft across the Syrian border to help U.S.-backed rebels drive Islamic State militants out of the key border town of Jarabulus. But equally high on the Turkish agenda was preventing U.S.-supported Syrian Kurdish forces fighting the Islamic State from occupying Jarabulus and the surrounding border area.

Russian media reported Friday that Moscow has asked Turkey for information on its air operations inside Syria. The Russian Defense Ministry wants “to prevent air incidents because it will be the first time when Turkish warplanes will intensively bomb targets in Syria and may meet Russian warplanes in midair,” a ministry official said, according to the newspaper Izvestia.

The United States and Russia already have a “deconfliction” agreement to avoid collisions in the increasingly crowded Syrian skies.

Separate from the coordination deal, Russia has proposed a weekly, 48-hour pause in fighting in Aleppo that would allow aid deliveries to the rebel-held eastern part of the city along the Castello Road, the main rebel and aid supply line north to Turkey that was cut weeks ago by Russian and Syrian bombardment.

In response, a Front-led offensive pushed through government lines to the city’s rebel south and is now attacking government-held western Aleppo.

Staffan de Mistura, the U.N. special envoy for Syria, said U.N. aid convoys are loaded and ready to move into the city. “We want a pause for 48 hours,” he said. “The Russian Federation replied ‘yes.’ We will wait for others to do the same. But we are ready, trucks are ready, and they can leave anytime we get that message.”

But rebel groups have yet to agree to the proposal.

Heba Habib in Stockholm contributed to this report.