Washington has announced it is ready to respond with hard-hitting sanctions if Russia invades Ukraine.
US Secretary of State Antony Blinken has met with his Russian counterpart to warn him face-to-face of the "serious consequences" Russia would suffer if it invaded Ukraine and to urge him to seek a diplomatic exit from the crisis.
Blinken delivered the warning to Russian Foreign Minister Sergey Lavrov at a meeting on Thursday in Stockholm, a day after declaring that Washington was ready to respond resolutely, including with hard-hitting sanctions, in the event of a Russian attack.
"The best way to avert the crisis is through diplomacy and that's what I look forward to discussing with Sergey," Blinken told reporters before going into talks with Lavrov.
He said Russia and Ukraine should each fully implement their obligations under the 2014 Minsk peace process, which was designed to end a war between pro-Russian separatists and Ukrainian government forces in the east of the former Soviet republic.
Washington was willing to facilitate this, Blinken said, but "if Russia decides to pursue confrontation, there will be serious consequences".
Lavrov told reporters Moscow was ready for dialogue with Kiev. "We, as President Putin has stated, do not want any conflicts."
Ukraine has become the main flashpoint between Russia and the West as relations have soured to their worst level in the three decades since the Cold War ended.
Kiev says Russia has amassed more than 90,000 troops near their long shared border.
Moscow accuses Kiev of pursuing its own military build-up.
It has dismissed suggestions that it is preparing for an attack on Ukraine as inflammatory and has defended its right to deploy troops on its own territory as it sees fit.
The Kremlin said on Thursday that the probability of a new conflict in eastern Ukraine remained high and that Moscow was concerned by "aggressive" rhetoric from Kiev.
Russia also said on Thursday it had arrested three suspected Ukrainian intelligence agents, including one accused of planning to carry out an attack using two homemade bombs, allegations that Kiev dismissed.
Last week Ukraine's president said Kiev had thwarted a Russian-backed coup plot, which the Kremlin denied.
In a speech to the Organisation for Security and Cooperation in Europe earlier on Thursday, Lavrov said military tensions were rising on the continent and he hoped that Russia's proposals on a new European security pact would be carefully considered.