GENEVA — The US has agreed to respond to Russia's demands over NATO positions in Europe in writing next week, Sergei Lavrov said on Friday after a second round of talks over Ukraine.

Russia's foreign minister described his two-hour discussion with his US counterpart, Antony Blinken, as "constructive, useful".

He, however, refused to characterise Washington's promise of a written response as a positive step.

“I can’t say whether we are on the right path or not. We will see when we get the American responses," he said.

Blinken is set to speak to reporters shortly.

The meeting in Geneva, Switzerland, which sought to de-escalate the crisis at the Ukrainian border, came 11 days after the first round of discussions in the Swiss city yielded little result.

Russia has amassed some 100,000 troops on the border and is being accused by the US of planning an invasion, which it denies.

Instead, it accuses the West of plotting “provocations” in Ukraine, citing the delivery of weapons to the country by British military transports in recent days.

Russia wants binding security guarantees, including a permanent prohibition on Ukrainian membership in NATO, to which Kyiv aspires, and the removal of most of the US and allied military presence in eastern Europe.

Washington, Brussels and NATO have rejected these demands and warned that any attack on Ukraine would have costly consequences.

Both Blinken and Lavrov had muted expectations ahead of their sit-down, stressing that any breakthrough was unlikely.

Just 20 minutes before the start of the meeting, Moscow announced that it wants foreign NATO troops out of Romania and Bulgaria as part of any treaty.

Bucharest has categorically rejected this demand. The Foreign Ministry said in a statement that Russia's request for NATO troops to be reduced in all states that joined the alliance after 1997 is "unacceptable and cannot be the subject of negotiation, given that the deterrence and defence posture if inextricably linked to, and an intrinsic part of, NATO's collective defence mechanism, over which no third state can have a veto."

It added that NATO troops' presence in allied countries "is a strictly defensive reaction to the increasingly aggressive behaviour of the Russian Federation in the Eastern Neighbourhood, especially since 2014 when the Ukrainian territory of Crimea was illegally occupied by Russia."

On Thursday, the Kremlin had denounced as "destabilising" remarks by US President Joe Biden on Wednesday that promised a severe response from the US and its allies in case of a Russian military incursion into Ukraine. Moscow argued Biden's comments could give ideas to "hotheads among Ukrainian officials".

Blinken arrived in Geneva after a whirlwind tour that took him from Kyiv to Berlin, the city that symbolised the reunification of Europe after the Cold War, for talks with German, French and British allies.

"To allow Russia to violate those principles with impunity would drag us all back to a much more dangerous and unstable time, when this continent - and this city - were divided in two, separated by no man's lands, patrolled by soldiers, with a threat of all-out war hanging over everyone's heads," he said from Berlin.

"It would also send a message to others around the world that these principles are expendable and that too would have catastrophic results," he added.

In initial talks last week in Switzerland, US Assistant Secretary of State Wendy Sherman proposed building on the defunct Intermediate-range Nuclear Forces (INF) disarmament treaty signed during the Cold War with Moscow.

In 2019, former US President Donald Trump withdrew from the treaty, accusing Russia of violations.

Biden said on Wednesday he was ready for a new summit with Vladimir Putin, after the one on 16 June 2021, also in Geneva.

Russia did not say no to the proposals on missiles and manoeuvres but reiterated that this was not the main issue. For good measure, it announced on Thursday large-scale naval manoeuvres in January and February in the Atlantic, Arctic, Pacific and Mediterranean.

The head of US diplomacy urged Putin on Wednesday to choose the "peaceful path" and he also made it clear that he would not propose written answers to the very detailed demands made a few weeks ago by the Russians on the points of contention. — Agencies