A top Kremlin foreign-policy adviser has threatened retaliatory measures against U.S. officials in response to Washington's closure of Russian diplomatic property in the United States last year.
Yury Ushakov's comments on May 12 signaled a possible reversal in policy by the Kremlin regarding the closure, which was announced in December by then-President Barack Obama.
Obama ordered two diplomatic compounds in Maryland and New York closed, and the expulsion of 35 Russian personnel as retaliation for Russia's alleged hacking during the 2016 presidential election.
Russian President Vladimir Putin surprised most observers a day later, when he said Russia would not do any tit-for-tat expulsions. That move was later praised by President Donald Trump.
Earlier this week, Deputy Foreign Minister Sergei Ryabkov met in New York with his U.S. counterpart, acting Deputy Secretary of State Tom Shannon. The two discussed, ways to improve strained relations between the two countries, including lifting the closure order on the diplomatic compounds, according to a post on the Foreign Ministry Facebook page.
On May 12, Ushakov told reporters in Moscow that Russia might retaliate against U.S. personnel if the compounds weren't released.
"We are demonstrating patience," Ushakov was quoted as saying by Russian news agencies. Obama's order, he said, "simply does not lend itself to any sort of understanding, but our president has reacted calmly and carefully."
"We decided not to respond immediately to this escapade, but no one has yet abolished the principle of reciprocity in diplomacy.... Our patience is not without limits," he said.
"The improvement in the atmosphere of bilateral relations largely depends on the removal of the numerous irritants set up by Washington in recent years; in particular, we are waiting for the return of Russian diplomatic property," he said.
Ushakov did not specify what measures Russia might take. In the past, however, the U.S. State Department has frequently complained about its diplomats being harassed in Russia.
Ushakov also said the issue was raised by Russian Foreign Minister Sergei Lavrov in his White House meeting with Trump on May 10.
With reporting by TASS and Interfax