By Andreas Rinke, Denis Pinchuk and Natalia Zinets

BERLIN (Reuters) - Germany and France pressed Russian President Vladimir Putin to extend a pause in air strikes in Syria and halt the "criminal" bombardment of civilians, but said four-way talks aimed at ending violence in eastern Ukraine made some progress.

"We are talking here about criminal activities, about crimes against the civilians," German Chancellor Angela Merkel told reporters after what she described as a difficult discussion with Putin about the crisis in Syria.

French President Francois Hollande used the phrase "war crimes," and both leaders criticized Russia for attacking the civilian population under the pretense of fighting terrorism.

"We agree that terrorism must be combatted, but not at the price that 300,000 people there must lose their lives and suffer without all necessary supplies," Merkel said, reflecting growing concern in Europe and the United States about Russia's support for Syrian President Bashar al-Assad.

Merkel and Hollande will discuss the talks at an EU summit meeting on Thursday evening, with the bloc due to consider whether to impose new sanctions on Russians over the bombing in the besieged Syrian city of Aleppo.

While there is no immediate consensus for more sanctions, Britain and France, with support from eastern and Nordic countries, said they could push for them in the coming weeks if Russia continues to bomb the rebel-held east of the city.

Merkel said she could not rule out sanctions, but said Thursday's EU meeting would be focused on helping civilians.

"We made it very, very clear tonight that Russia has a great responsibility that extends far beyond the bombardment," she said. "It will decide whether humanitarian supplies can be delivered (and) whether a political process can be begun."

Putin told a separate news conference that Moscow had proposed to speed up adoption of a new constitution in Syria to facilitate future elections, and said Russia was ready to extend an eight-hour pause in air strikes in Syria.

He underscored the importance of "eradicating terrorism" and called on the United States to separate Al Nusra Front militants from what he called "the healthy opposition" in Syria.

Hollande acknowledged Putin's offer of extending the ceasefire, but said a longer pause in bombing was needed to bring in much-needed humanitarian supplies.

"A respite of a few hours makes no sense," he told a joint news conference with Merkel after the talks. "The main point is that the population of Aleppo ... cannot continue to live in conditions that are unbearable."

Merkel had insisted that Putin agree to discuss Syria on the sidelines of the so-called "Normandy Format" meeting on Ukraine. It was the Russian leader's first trip to Germany since 2013.

The meeting took place hours after news emerged that Russian warships off the coast of Norway were preparing to reinforce a brutal assault on Aleppo.

PROGRESS ON UKRAINE, HARD WORK AHEAD

Merkel said a separate meeting with Hollande, Putin and Ukrainian President Petro Poroshenko - their first in over a year - had resulted in agreement on a preliminary road map for implementing the Minsk peace deal reached in February 2015.

Foreign ministers will work out details of the plan in November, but hard work remained ahead, Merkel said.

Poroshenko said the sides agreed during the five-hour meeting to withdraw Ukrainian troops and Russian-backed separatists from four new areas at the frontline of the fighting in the Donbass region. That follows the withdrawal of forces from three other key areas that began last month.

They also agreed that monitors from the Organization for Security and Co-operation in Europe (OSCE) could be armed and that their activities in monitoring the so-called Minsk peace process would not be impeded.

Local elections remained a matter of debate, with Ukraine insisting it would only hold elections in the Donbass region after foreign forces withdrew, Poroshenko told reporters.

Separatist violence erupted in eastern Ukraine in 2014 and has killed 9,600 people so far. Both Russia and Ukraine accuse each other of perpetuating the violence and violating the 2015 Minsk peace agreement.

At Thursday's EU dinner, eastern and Baltic countries are also set to call for stronger EU defenses against what they say is Russian disinformation campaigns to destabilize their governments or a possible cyber attack.

"The mood is hardening," said a senior EU diplomat. "Russia used to be seen as a strategic partner. Now it is a strategic problem."

(Reporting by Natalia Zinets, Denis Pinchuk, Andreas Rinke, Andrea Shalal and Paul Carrel in Berlin, and Robin Emmott in Brussels; Writing by Andrea Shalal; Editing by Mark Heinrich and Lisa Shumaker)