GENEVA, Switzerland — US Deputy Secretary of State Wendy Sherman said she does not know yet whether Russia is prepared to de-escalate the situation with Ukraine following its massive build-up of Russian troops near Ukraine's border and fears of a possible invasion.

Sherman met with Russian Deputy Foreign Minister Sergey Ryabkov on Monday in the first of three sets of bilateral talks slated for this week. She told reporters that the session was "frank and forthright" but that it is too soon to say whether the Kremlin was serious about diplomacy.

"I don't think we know the answer to that," Sherman said when asked if the US got an indication that Russia is prepared to de-escalate on the Ukrainian border. "We will see whether in fact Russia understands that the best way to pursue diplomacy is for them to reduce those tensions and to de-escalate."

The talks, which wrapped up Monday after more than seven hours in Geneva, Switzerland, follow months of tension near the Ukraine-Russia border, where more than 100,000 Russian soldiers have massed.

Ryabkov told reporters after the meeting that despite American concerns about the Russian troop build-up along the Ukrainian border, Moscow had no intention of launching military action.

"We explained to our colleagues that we have no plans to attack," he said. "All the combat trainings of troops are carried out within our national territory, and there is no reason to fear any escalation scenario in this regard."

Sherman said that the US "certainly urged Russia to deescalate" adding: "But we will see." She said that the US did not set specific timelines for anything.

Sherman said the US defines de-escalation as Russia returning its thousands of troops on the border with Ukraine to their barracks or explaining what exercises they are conducting and what their purposes are. The Russians told the US that the massing of troops on the border was not a precursor to an invasion, she said.

"I don't think you'd be surprised to hear that Russia indeed said to us as they said publicly, they do not intend to invade, these are just maneuvers and exercises," Sherman said. "And they can prove that in fact they have no intention by deescalating and returning troops to barracks," she said.

Monday's talks were the first of three sets of meetings on tap this week, with NATO talks with Russia on Wednesday in Brussels, followed by talks Thursday in Vienna between Russia and the Organization for Security and Cooperation in Europe (OSCE).

The US and Russia had "useful discussions" on Monday, Sherman said, but they did not negotiate about specifics. Sherman said the US delegation pushed back on Russian proposals that were "simply nonstarters," such as Russia's demand in the lead-up to this week's sessions that NATO pledge never to admit Ukraine, saying that "we will not allow anyone to slam closed NATO's open door policy."

Sherman again stressed the US would not have discussions about Ukraine or Europe without those partners in the room.

Ryabkov dscribed the hours-long talks as "business-like" and "professional." Nonetheless, he said, "The main questions hang in the air, and we do not see that the American side has any understanding of the imperative of their solution, as to what suits us."

Sherman said that the US delegation expressed openness to discussing the future of certain missile systems in Europe along the lines of the now-defunct Intermediate-Range Nuclear Forces (INF) Treaty, as well as ways that both sides could set "reciprocal limits on the size and scope of military exercises" and to improve transparency about those exercises.

She noted that both the US and Russia understand that issues as complicated as arms control will take longer than a few days or weeks. Sherman said the US would have further conversations with the Russian government after the multilateral discussions this week.

Deputy National Security Adviser Jon Finer told CNN's Jim Sciutto on Monday as the talks wrapped that he does not "see a situation in which the US walks away" from talks with Russia, even if Kremlin officials take positions during this week's discussions that are considered nonstarters by the US.

"Russia put out positions that are non-starters and said other things we think maybe present some areas in which we can work to make progress, and we're going to find that out during the course of this week," Finer said.

Russian demands, released publicly a few weeks before the talks, include that NATO not expand further east and pledge to never admit Ukraine as a new member.

Asked whether success requires Russia pulling back its forces from the border with Ukraine, Finer said he would not be "setting the bar on the negotiating team while the talks are still under way."

"This is the first opportunity we've had at a high level to explore and understand better what is Russia's position, what are Russia's intentions, to better understand where we are coming from," he said.

The global community will be closely following the discussions, which have been billed as a late attempt to avert a war on Europe's eastern flank.

Still, Secretary of State Antony Blinken played down the prospects of a breakthrough on the eve of the talks.

"It's hard to see making actual progress, as opposed to talking, in an atmosphere of escalation with a gun to Ukraine's head.

“So, if we're actually going to make progress, we're going to have to see de-escalation, Russia pulling back from the threat that it currently poses to Ukraine," Blinken said on CNN's "State of the Union" on Sunday.

"We're here because repeatedly over the last decade, Russia has committed acts of aggression against neighbors — Georgia, Moldova, Ukraine in 2014, and now the renewed threat about Ukraine today," he added.

"It's also not about making concessions. It's about seeing whether, in the context of dialogue and diplomacy, there are things that both sides, all sides can do to reduce tensions," Blinken said.

On Sunday, Sherman and Ryabkov held a dinner that was "difficult but business-like" ahead of Monday's formal session, Ryabkov told state news agency RIA Novosti.

"Initially, it was clear that their line was to immerse our ideas, our proposals and our approaches in the technological environment from the point of view of diplomacy that has developed over the past decades."

The State Department readout of the dinner said 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."

As many as 100,000 Russian troops have remained gathered near the Ukrainian border, despite warnings from US President Joe Biden and European leaders of serious consequences should Putin move ahead with an invasion.

And US intelligence findings estimated last month that Russia could begin a military offensive in Ukraine "as soon as early 2022."

Biden told Ukrainian President Volodymyr Zelensky in a phone call earlier this month that the US and its allies "will respond decisively if Russia further invades Ukraine." — CNN