No breakthrough in four-way 'Normandy' talks on Ukraine

Presidential advisers from Russia, Ukraine, France and Germany have met for more than eight hours over the long-running Ukraine conflict, and reached no breakthrough, but promised to meet for new talks in two weeks in Berlin.

Russia's chief negotiator, Dmitry Kozak, told reporters on Wednesday that many issues concerning a peace settlement for the conflict in eastern Ukraine remained unresolved after eight hours of talks.

But he said he hoped positions could be narrowed.

Diplomats, who met for 'Normandy talks' in Paris, in a joint statement reaffirmed their commitment to upholding the ceasefire agreed in the so-called Minsk accords.

"They support unconditional compliance with the ceasefire(...) regardless of differences on other issues related to the implementation of the Minsk agreements", they said in a statement published on the website of the French presidency. 

Russia said another round of talks will take place in Germany.

Talks between Russia and Ukraine in Paris were "not simple" but a new round of discussions will take place in two weeks in Berlin, Kozak said.

The conflict in eastern Ukraine pits Kiev's forces against Russian-backed separatists and has raged since 2014.

READ MORE: EU plans to back Ukraine with $1.36 billion aid package

No concessions from US

Meanwhile, the US has made no concessions to the main Russian demands over Ukraine and NATO in a long-awaited written response delivered to Russia on Wednesday in Moscow, Secretary of State Antony Blinken said.

Blinken said the US response, delivered to the Russian Foreign Ministry by US ambassador to Russia John Sullivan, gave up no ground on "core principles" such as NATO's open-door membership policy and the alliance's military presence in Eastern Europe.

Blinken said the document made clear that the US is standing by its oft-stated positions. "There is no change, there will be no change," he said. But, he said the written response to Russia also contains "serious" offers for a diplomatic path to de-escalate soaring tensions over Ukraine by addressing Russian concerns on other matters.

Russia has warned it would quickly take "retaliatory measures" if the US and its allies rejected its demands.

READ MORE: US asks diplomats' families to depart Ukraine over Russia threats

NATO's response to Russia

The US proposals, echoed in a separate document sent to the Russians by NATO, include the potential for negotiations over offensive missile placements and military exercises in Eastern Europe as well as broad arms control agreements as long as Russia withdraws its estimated 100,000 troops from the Ukrainian border.

Moscow has demanded guarantees that NATO will never admit Ukraine and other ex-Soviet nations as members and that the alliance will roll back troop deployments in former Soviet bloc nations. 

Some of these, like the membership pledge, are nonstarters for the US and its allies, creating a seemingly intractable stalemate that many fear can only end in a war.

The Kremlin has repeatedly denied it has plans to attack Ukraine, but the US and NATO are worried about Russia massing its troops near Ukraine and conducting a series of sweeping military maneuvers.

READ MORE: Russia threatens retaliation if West rejects demands over NATO, Ukraine