WASHINGTON - The Kremlin said Tuesday it has little optimism about a breakthrough on talks with the United States this week about its European security concerns, while Washington said Moscow's massive troop buildup along the Ukraine border is at the root of current tensions.

After a day of talks with U.S. diplomats Monday in Geneva, Moscow said it would wait for the outcome of more meetings set for Wednesday in Brussels and Thursday in Vienna before deciding whether it's worth it to continue negotiations with Washington officials.

FILE - Victoria Nuland, undersecretary of state for political affairs, speaks on Capitol Hill, Dec. 7, 2021

But in the U.S., Victoria Nuland, undersecretary of state for political affairs, told reporters, 'We haven't seen the slightest hint of de-escalation' on Russia's part. 'It is Russia that created this crisis out of whole cloth' by deploying 100,000 troops just across from Ukraine's eastern border.

At the Geneva talks, Russia demanded guarantees, rejected by Washington, that the West's 30-country NATO military alliance halt further eastward expansion toward Russia and curb military deployments in Eastern Europe.

'NATO poses no threat to Russia. It is a defensive alliance whose sole purpose is to protect its members,' Nuland said.

Kremlin spokesman Dmitry Peskov said the first day of talks in Geneva were 'open, comprehensive and direct,' an assessment echoed by Washington. But Peskov said it was the result that ultimately matters.

FILE - Kremlin spokesman Dmitry Peskov attends a news conference in Moscow, Russia, Dec. 23, 2021.

'So far, let's say we see no significant reason for optimism,' he said in a conference call with reporters.

NATO and Russia are holding talks in Brussels, while the Organization for Security and Cooperation in Europe is meeting in Vienna.

'There are still several rounds [of talks] ahead of us, which will allow us to work out a clearer understanding, a clearer picture of where we stand with the Americans,' Peskov said.

He said Russia is not setting deadlines for the talks but also would not accept dragging them out.

Western allies fear that Russia is planning to invade Ukraine after annexing its Crimean Peninsula in 2014. Russia has denied it plans to invade its one-time Soviet satellite state but also has not acceded to U.S. demands that it withdraw troops from the border.

U.S. President Joe Biden has ruled out a military confrontation with Russia in the event it decides to attack Ukraine but says the U.S. and its allies would impose significant economic sanctions if it does invade.

FILE - U.S. Deputy Secretary of State Wendy Sherman, left, and Russian deputy foreign minister Sergei Ryabkov attend security talks at the United States Mission in Geneva, Switzerland, Jan. 10, 2022.

U.S. Deputy Secretary of State Wendy Sherman, who led the U.S. delegation in Geneva, said Tuesday on Twitter, 'The United States is committed to working in lockstep with our allies and partners to urge de-escalation and respond to the security crisis caused by Russia.'

In Monday's bilateral talks, the two parties discussed 'reciprocal action that would be in our security interest and proved strategic stability,' Sherman said. That includes possible limits on both sides on the size and scope of future military exercises in the region.

European Council President Charles Michel reiterated that 'we have clearly said that if there was to be a military offensive against Ukraine, there would be a massive reaction from the European Union in coordination with our partners and allies.'

Estonian Defense Minister Kalle Laanet called the Russian demands to curb NATO expansion, if it wishes to do so, 'completely unacceptable,' adding that he expects the alliance members at Wednesday's meeting to 'be very clear in saying that ... NATO's collective defense continues to be a value that is being defended by its members.'

In Geneva, Russian negotiator Sergei Ryabkov rejected U.S. demands that Moscow pull back its estimated 100,000 troops from the Ukrainian border, saying it had the right to deploy them wherever it wanted.

Some material in this report came from The Associated Press.