Russia has told the United States at tense talks that it has no plans to invade Ukraine, as the two sides agreed to more efforts to keep tensions from turning into a full-blown confrontation.
After more than seven hours of negotiations in Geneva, the Russian and US negotiators both offered to keep talking, though there was no sign of a major breakthrough.
The high-stakes negotiations came amid fears of a Russian invasion of its pro-Western neighbour Ukraine, and with Moscow demanding wide-ranging concessions from Washington and its NATO allies.
Russian Deputy Foreign Minister Sergei Ryabkov said he had assured his US counterpart, Deputy Secretary of State Wendy Sherman, that those fears were unfounded.
"We explained to our colleagues that we have no plans, no intentions to 'attack' Ukraine... There is no reason to fear any escalation in this regard," he told reporters after the talks.
Mr Ryabkov said the United States "took Russian proposals very seriously" and that Moscow was "for the continuation of dialogue".
Ms Sherman said that she offered to make reciprocal moves with Russia on missiles and exercises, but renewed warnings of major costs if Moscow invaded Ukraine.
'Non-starters' for US
She said the United States was ready to meet again, but that Russia had not offered assurances that it will pull back troops amassed near Ukraine.
And she insisted that some of Russia's demands were "simply non-starters", including a ban on NATO's further eastward expansion.
"We will not allow anyone to slam closed NATO's open-door policy," Ms Sherman said.
Monday's talks in Geneva launched a week of diplomacy between Russia and the West after Moscow amassed tens of thousands of troops at the Ukrainian border, drawing the United States into a Cold War-style stand-off.
Both sides have set firm lines, with Washington warning that Moscow would face severe diplomatic and economic consequences from an invasion of Ukraine, and Russia demanding broad new security arrangements with the West.
After today's talks, a meeting of the NATO-Russia Council will take place in Brussels on Wednesday, then the permanent council of the Organization for Security and Cooperation in Europe (OSCE) will meet in Vienna on Thursday with the issue of Ukraine expected to dominate.
Sherman renewed a call on Russia to pull back its estimated 100,000 troops.
If Russia invades, she said, "there will be significant costs and consequences, well beyond what they faced in 2014," when Moscow seized the Crimean peninsula and backed an insurgency in eastern Ukraine.
Mr Ryabkov denounced US threats as "attempts at blackmail and intimidation", but said "I don't think the situation is hopeless".
'Severe costs' of invasion
Any direct military action by the United States or NATO in defence of Ukraine is extremely unlikely.
But Western officials have warned Moscow would face significant economic and financial consequences if it invades, and could see NATO boost its presence and capacities near Russia's borders.
NATO chief Jens Stoltenberg said today that the alliance would be warning Russia of the "severe costs" of an invasion.
He said he did not expect this week's talks to "solve all the issues", but wanted to kickstart a diplomatic process.
"We are aiming for an agreement on a way forward, a process, a series of meetings," Stoltenberg said before talks with Ukraine's deputy prime minister in Brussels.
Measures against Russia under consideration include sanctions on President Vladimir Putin's inner circle, cancelling Russia's controversial Nord Stream 2 pipeline to Germany or, in the most drastic scenario, severing Russia's links to the world's banking system.
'Soviet Union 2.0'
Moscow insists it was deceived after the Cold War and understood that NATO would not expand eastward.
Instead, the US-led alliance welcomed most of the former Warsaw Pact countries and the three Baltic nations that were under Soviet rule.
Russia has put intense pressure on Ukraine since 2014 after a revolution overthrew a government that had sided with the Kremlin against moving closer to Europe.
Russia seized the Crimean peninsula and backs an insurgency in eastern Ukraine in which more than 13,000 people have died.
The heaviest of the fighting has subsided but clashes continue almost daily, with the Ukrainian army saying Monday that two of its soldiers died after an explosion from an unknown device.
The army also accused separatist forces of firing at its positions with grenade launchers, machine guns and small arms.
In the muddy trenches on the frontline, there was little hope for diplomacy.
"I doubt that anything will change," 29-year-old soldier Mykhailo said as he walked through trenches in the town of Avdiivka, just north of the separatist stronghold city of Donetsk.
"Guarantees of not joining NATO will never stop" Putin, Mykhailo said, adding: "He wants to return the Soviet Union in version 2.0."
Security concerns 'increasingly pressing'
Russia's ambassador to Ireland has said the issue of the security of Russia's western borders is becoming increasingly pressing.
Speaking on RTÉ's Six One News, Yuriy Filatov said his country can no longer tolerate the instability and military threat which is growing on its western borders and it is demanding legally binding guarantees for Russia's national security from NATO, the US and its allies.
He said this is not an issue about Ukraine's sovereignty but an issue of Russian national security.
NATO has been steadily expanding eastwards with all the military infrastructure and making even more troubling declarations that there is a threat from Russia which needed to be contained, Mr Filatov claimed.