Russia and the United States failed to make any major progress in a row over the functioning of their embassies at talks in Moscow on Tuesday and there is a risk that relations could worsen further, Russia's Deputy Foreign Minister Sergei Ryabkov said.
With ties already at post-Cold War lows, the two countries are in dispute over the workings of their diplomatic missions, including the number of diplomats they can post to each other's capitals.
"I cannot say that we have achieved great progress," Interfax news agency quoted Ryabkov as saying after the talks with US under Secretary of State Victoria Nuland. "There is a risk of further sharpening of tensions."
There was no immediate comment from the US side.
Last week the Russian foreign ministry said a US congressional proposal to expel 300 Russian diplomats from the United States would lead to the closure of US diplomatic facilities in Russia, if implemented.
Ryabkov said the conversation with Nuland was open and useful, but the two parties' positions remain at odds.
Moscow does not rule out the work of Russian and US diplomatic missions being frozen, but would like to avoid such a scenario, the RIA news agency cited Ryabkov as saying.
He said the two sides would hold new consultations on resolving the issue around visas and diplomats, without specifying a date.
Nuland's visit to Moscow this week angered some Russian nationalists who ransacked a makeshift memorial to slain Kremlin critic Boris Nemtsov in central Moscow early on Monday.
The veteran Russia specialist is regarded by Kremlin hawks as someone who has stirred up anti-Russian sentiment in former Soviet countries such as Ukraine that Moscow considers its sphere of influence.
Her visit comes at a time when ties between the US and Russia are badly strained over a host of other issues, including cyberattacks against US targets and the jailing of Alexei Navalny, the most prominent domestic opponent of President Vladimir Putin.