Ukraine and Russia have agreed to implement a "full and comprehensive" ceasefire in eastern Ukraine by the end of 2019, after top-level talks.
Russian President Vladimir Putin and Ukraine's Volodymyr Zelensky met face to face at a Paris summit on Monday.
Mr Zelensky was downbeat, saying little had been achieved at the meeting and he had wanted to see more resolved.
Five-and-a-half years of fighting between Ukrainian forces and Russian-backed rebels have cost 13,000 lives.
The negotiations were brokered by the leaders of France and Germany.
They follow a big prisoner swap and the withdrawal of Ukraine's military from three key areas on the front line.
Here’s the full Normandy Summit communique... it’s not long. pic.twitter.com/0nI0MpaQyy— Jonah Fisher (@JonahFisherBBC) December 9, 2019
What was agreed?
In a written statement, the countries agreed to the release and exchange of all "conflict-related detainees" by the end of the year.
The two sides also pledged to disengage military forces in three additional regions of Ukraine by the end of March 2020, without specifying which regions would be affected.
Additional talks will be held in four months to take stock of the ceasefire's progress.
At a press conference after the talks in France's Elysée Palace, President Putin hailed them as an "important step" towards a de-escalation of the conflict.
President Zelensky said the issue of Russian gas exports via pipelines through Ukraine had been "unblocked" after a dispute about transit tariffs, and an agreement would now be worked out.
But Russia and Ukraine continue to disagree on issues such as the withdrawal of Russian-backed troops, and elections in areas of Ukraine held by the separatist rebels.
Mr Putin also called for a change in Ukraine's constitution to give special status to the Donbas region, which is held by the rebels. He also pushed for an amnesty for people who had taken part in the seizure of Ukrainian territory.
Mr Zelensky told reporters that Ukraine would not make any territorial concessions in exchange for peace.
"We saw differences today," said French President Emmanuel Macron, who hosted the talks with German Chancellor Angela Merkel.
"We didn't find the miracle solution, but we have advanced on it," he added.
So how did we get here?
Mr Zelensky, a former comic actor, was elected president of Ukraine in a landslide victory in April following a campaign built around bringing peace to eastern Ukraine.
Since then, his strategy has focused on trying to restart talks with Moscow. For that to happen Mr Zelensky has had to agree to some Russian conditions, including pulling back Ukrainian troops in the eastern towns of Stanytsia Luhansk, Petrivske, and Zolote.
In June, Ukrainian troops and pro-Russian separatists withdrew a kilometre from Stanytsia Luhanska. By late October, the Ukrainians and separatists had disengaged from Zolote and early in November they pulled back from Petrivske.
Nato and Western intelligence experts have repeatedly accused Russia of sending heavy weapons and combat troops into eastern Ukraine to help the rebels.
Russia denies that, but admits that Russian "volunteers" are helping the rebels.
In September, Mr Zelensky won praise for a long-awaited prisoner swap with Russia - he described it as a "victory" that had emerged from personal phone contact with the Russian president.
To pave the way for the summit, President Zelensky accepted a 2016 deal granting special status to the separatist-held parts of Ukraine's Donbas region.
The "Steinmeier formula" aims to break the impasse over peace agreements reached at the height of the fighting. It details free and fair elections in the east under Ukrainian law, verification by the Organisation for Security and Co-operation in Europe (OSCE), and then self-governing status in return.
What triggered the deadly conflict?
Pro-Russian separatists seized control of large swathes of Donetsk and Luhansk regions in April 2014, just after Russia's annexation of Ukraine's Crimea peninsula.
It was an insurgency against the new pro-Western authorities in the capital Kyiv, who had ousted the pro-Russian President, Viktor Yanukovych, in street protests dubbed the "Maidan Revolution".
The separatists later declared independence from Ukraine - but no country has recognised their "republics".
- March, 2014: Russian forces annex Crimea after President Yanukovych is ousted in Kyiv, prompting the biggest East-West showdown since the Cold War. The US and the EU impose harsh sanctions on Russia
- April: Pro-Russian armed groups seize parts of the Donetsk and Luhansk regions on the Russian border of eastern Ukraine. Ukraine launches a military operation in response
- September: Nato confirms Russian troops and heavy military equipment have been entering eastern Ukraine
- November, 2018: Three Ukrainian ships are intercepted by Russia in the Kerch Strait near Crimea. Ukraine calls it an act of Russian aggression, saying the Black Sea is free for shipping
- April-July, 2019: Volodymyr Zelensky wins presidential election run-off in a landslide victory over incumbent Petro Poroshenko
- September: Russia and Ukraine swap prisoners captured in the wake of Moscow's seizure of Crimea and intervention in the Donbas
- November: Russia returns three navy boats to Ukraine almost a year after they were seized off the Crimean Peninsula