Russia warned that it would walk away from diplomatic efforts to end the crisis over Ukraine if the west continued to ignore demands over security guarantees, but agreed to extend talks into this week.

There was no breakthrough in Geneva after nearly eight hours of discussions between Wendy Sherman, US deputy secretary of state, and Sergei Ryabkov, Russia’s deputy foreign minister, in which the American side presented new ideas on arms control.

But there was no breakdown either in talks that Russia has warned could lead to military action if its red lines are not respected. With 100,000 Russian troops amassed along its border with Ukraine, fears of conflict have intensified.

The US and Nato ruled out Moscow’s top demand for a ban on Nato enlargement. Sherman said Russia still had a choice between diplomacy and escalation, with the outcome still in the balance.

‘If Russia walks away from the diplomatic path, it may well be quite apparent that they were never serious about pursuing diplomacy at all,” she said.

Recommended Ryabkov said Moscow “will judge any further steps and the prospects of all this work and make appropriate decisions based on the results of events that are still to come in the coming days” regarding whether it was worth continuing talks.

Russia began the day warning that it walk away from the talks if the west continued to ignore its demands over Nato expansion.

Russian officials will hold talks with Nato in Brussels on Wednesday and with the 57-member Organisation for Security and Co-operation in Europe on

Thursday in Vienna. Sherman said she would then “have further conversations with the Russian government and decide on the best way forward” later in the week.

She described the talks as “serious, straightforward business, candid discussion”.