The White House has said it is "too early" to know whether Russia is serious about resolving security tensions in and around Ukraine.
Tensions around Ukraine have escalated in recent months, as the United States and Ukraine's European allies accuse Russia of threatening the former Soviet country with invasion.
After talks with US diplomats in Geneva and with more negotiations to come in Brussels, "it's too early to tell whether the Russians are serious about the path to diplomacy or not," Press Secretary Jen Psaki told reporters.
Ms Psaki said it remained to be seen "if they're prepared to negotiate seriously - we are - or whether they'll use discussions as a pretext that diplomacy couldn't possibly work."
The next round of talks will be between NATO and Russia tomorrow, with a third session between the OSCE regional security body and Russia planned for Thursday.
The United States and its European allies are pressuring Russia to pull a large force back from the border with Ukraine, while Russia is pushing the West to agree to a long list of what they says are security guarantees.
Ms Psaki reiterated the US rejection of Russia's demand that Ukraine not be offered NATO membership one day, saying this is "a matter only for Ukraine and the 30 NATO allies, not for other countries to determine."
"There are a range of discussions that can be part of a diplomatic path but ultimately it's up to the Russians to determine about whether they're going to take a serious approach to it or not," she said.
Earlier, Ukraine said it welcomes "efforts" by the West and Russia to ease tensions after a week of high-stakes diplomacy kicked-off in Geneva yesterday.
"We can only welcome the intent and efforts of the United States and Russia, and NATO and Russia to reduce tensions and resolve all mutual issues at the negotiating table," Ukrainian President Volodymyr Zelensky's spokesman Sergiy Nykyforov said in a video statement.
After negotiations in Geneva yesterday, Russian and US officials offered to keep talking, but there was no breakthrough.
"We trust our partners and their statements that no decision on the fate of Ukraine will be taken behind our back," Mr Nykyforov said in the statement.
Ukraine is "interested in resolving the conflict" in the east of the country "as soon as possible" and "especially by peaceful means", he said.
Russia has put intense pressure on Ukraine since 2014 after a revolution overthrew a government that had sided with the Kremlin against closer ties with Europe.
Russia seized the Crimean peninsula and backs an insurgency in eastern Ukraine in which more than 13,000 people have died.
