Russia and US launch talks on European security

He also called the initial contact "amazing", according to Interfax, in what was understood as sarcasm.

Sherman "stressed the United States' commitment to the international principles of sovereignty, territorial integrity, and the freedom of sovereign nations to choose their own alliances," according to her office.

But the US would "welcome genuine progress through diplomacy," it added.

Ryabkov and Sherman will hold formal negotiations on Monday.

Nato and Russia will then hold high-level talks in Brussels on Wednesday and the Organisation for Security and Cooperation in Europe will conduct a third round of discussions in Vienna on Thursday.

It is unclear what, if any, role EU structures might play in the process.

The emergency meetings come after Russia massed troops around Ukraine late last year and the US warned Western allies that it planned an imminent attack.

Russia also demanded that Nato forbids entry to Georgia and Ukraine and removes international forces from the Baltic states and Poland, in demands called unacceptable by Western allies.

But new deals could be made on deployment of missiles and curbs on military drills, the West indicated.

For all that, US secretary of state Antony Blinken warned the public not to expect too much from this week's diplomacy.

"I don't think we're going to see any breakthroughs in the coming week," he told TV broadcaster CNN on Sunday.

"We're going to be able to put things on the table. Russians will do the same ... and we'll see if there are grounds for moving forward," he said.

"There are two paths before us. There's a path of dialogue and diplomacy to try to resolve some of these differences ... The other path is confrontation and massive consequences for Russia if it renews its aggression on Ukraine," he added.

"To make actual progress, it's very hard to see that happening when there's an ongoing escalation, when Russia has a gun to the head of Ukraine with 100,000 troops near its borders," Blinken also said on Friday.

The Nato secretary general, Jens Stoltenberg, said the same day, after meeting Nato foreign ministers in Brussels: "We can't end up in a situation where we have second-class Nato members, where Nato as an alliance is not allowed to protect them".

And he gave the lie to Russia's narratives on the crisis, indicating that the two sides remained far apart.

"The idea that Ukraine is a threat to Russia is to put the whole thing upside down," Stoltenberg said.

"Ukraine is not a threat to Russia. I think if anything, it is the idea of a democratic stable Ukraine which is a challenge for them," he said.

Kazakhstan jibes

Russia, last week, also sent troops to neighbouring Kazakhstan to help quell an uprising.

And for his part, Blinken noted on Saturday: "One lesson of recent history is that once Russians are in your house, it's sometimes very difficult to get them to leave".

But the Russian foreign ministry reacted angrily, in a sign of how nasty the Geneva and other talks could get.

"If Antony Blinken loves history lessons so much, then he should take the following into account: when Americans are in your house, it can be difficult to stay alive and not be robbed or raped," the Russian ministry said on its Telegram social-media channel.

"We are taught this not only by the recent past but by all 300 years of American statehood," it said.