Kremlin spokesman Dmitry Peskov said it was positive that Monday's talks in Geneva had been held in an open, substantive and direct manner, but Russia was interested only in results.
"There are no clear deadlines here, no one is setting them - there is just the Russian position that we will not be satisfied with the endless dragging out of this process," he said, according to Reuters.
Russia has pushed the West to the negotiating table after massing troops near Ukraine's border as it presses a set of far-reaching demands that would prevent Ukraine from ever joining NATO and roll back two decades of alliance expansion in Europe.
Washington has said it cannot accept these demands, although it is willing to engage on other aspects of Russia's proposals by discussing missile deployments or limits on the size of military exercises.
Peskov said the situation would be clearer after two further rounds of talks that Russia is due to hold this week – with NATO in Brussels on Wednesday and at the Organization for Security and Cooperation in Europe (OSCE) in Vienna on Thursday.
Russian and U.S. negotiators gave no sign of narrowing their differences in briefings after the first session in Geneva.
Russian Deputy Foreign Minister Sergei Ryabkov said the two sides had "in some ways opposite views". He told reporters: "For us it’s absolutely mandatory to make sure that Ukraine never, never, ever becomes a member of NATO."
U.S. Deputy Secretary of State Wendy Sherman said: "We were firm ... in pushing back on security proposals that are simply non-starters to the United States."
The United States urged Moscow to reverse its build-up of an estimated 100,000 troops near the border with Ukraine, which has prompted Ukrainian and Western concerns about a possible invasion.
Ryabkov said Russia had no intention of attacking Ukraine. Russian President Vladimir Putin has said the prospect of NATO admitting Ukraine as a member, or stationing weapons there that could strike Russia, is a "red line".
Ukraine wants to join NATO, which would come with a promise of protection from attack. The alliance has no immediate plans to admit it.