Russia said on Sunday it would not make any concessions under US pressure at talks this week on the Ukraine crisis and its demands for western security guarantees, and that there was a risk they might end quickly.

Talks are due in Geneva, Brussels and Vienna but the state-owned RIA news agency quoted deputy foreign minister Sergei Ryabkov as saying it was entirely possible that diplomacy could end abruptly after a single meeting.

“I can’t rule out anything, this is an entirely possible scenario and the Americans... should have no illusions about this,” he was quoted as saying. “Naturally, we will not make any concessions under pressure and in the course of threats that are constantly being formed by the western participants of the upcoming talks.”

Interfax news agency quoted Ryabkov, who will lead the Russian delegation in Geneva, as saying Moscow was not optimistic going into the talks. His comments signalled an uncompromising line from Moscow at the tensest point in US-Russian relations since the Cold War.

Tens of thousands of Russian troops are gathered within reach of the border with Ukraine in preparation for what Washington and Kyiv say could be a new invasion, eight years after Russia seized the Crimea peninsula from Ukraine.

Russia denies invasion plans and says it is responding to what it calls aggressive and provocative behaviour from the Nato military alliance and Ukraine, its former Soviet neighbour which has tilted towards the West and aspires to join Nato.

Last month Russia presented a sweeping set of demands including for a bar on further Nato expansion and an end to the alliance’s activity in central and eastern European countries that joined it after 1997.

The US and Nato have said large parts of the Russian proposals are a non-starter. A senior Joe Biden administration official on Saturday said the US was not willing to discuss limits on American troop deployments or the US force posture in Nato countries in the region.

It was ready, however, to talk about the possibility of each side restricting military exercises and missile deployments in the region. Russia’s foreign ministry said the team led by Ryabkov had arrived in Geneva, where the formal talks are due on Monday.

Russia is also due to hold negotiations with Nato in Brussels on Wednesday and at the Organisation for Security and Cooperation in Europe in Vienna on Thursday.