A Russian diplomatic compound, seized by the U.S. in 2016, sits abandoned in Upper Brookville, New York. (Andrew Gombert/EPA)

Russia said Friday that it is “ready to take reciprocal measures” if the United States does not return property in this country seized in December as part of the Obama administration’s response to Russian meddling in the U.S. election and harassment of American diplomats in Moscow.

Foreign Ministry spokeswoman Maria Zakharova told reporters that the allegations of interference and other accusations were “an obvious lie.”

She said Russia was also planning possible retaliation for the December expulsion of 35 Russian diplomats. “One of the easy options,” she said, would be to demand a reduction in the number of Americans assigned to the U.S. Embassy in Moscow, which she said far exceeds the number of Russians in Washington.

Thomas Shannon, the U.S. undersecretary of state for political affairs, and Russian Deputy Foreign Minister Sergei Ryabkov plan to meet in Washington on Monday to discuss issues including the expulsions and the seizure of two properties owned by the Russian government in this country. Then-President Barack Obama said that the resort compounds on Maryland’s Eastern Shore and on New York’s Long Island were being used for intelligence purposes.

An earlier meeting between Shannon and Ryabkov, scheduled for late June in Russia, was postponed “because the United States was not ready for meaningful discussion,” Zakharova said.

A 45-acre Russian diplomatic compound, seized by theU.S. in 2016 in connection with suspected Russian hacking activities, sits abandoned on the banks of the Corsica River near Centreville, Md. (Jim Lo Scalzo/EPA)

Russia has repeatedly denounced the compound seizures as violations of international law.

Recent indications that the Trump administration was preparing to return the properties brought criticism from Republican and Democratic lawmakers, who argue that Moscow has done nothing to warrant a reprieve from punishment for its meddling in the U.S. presidential election last year.

The interference, confirmed by U.S. intelligence agencies, and allegations of Trump campaign collusion with interests in Russia, remain under investigation by a special counsel and in Congress.

Administration officials have said that they consider the issue of the compounds a diplomatic squabble and that taking it off the table would enable greater cooperation with Russia in more important areas, including the war against the Islamic State in Syria.

Leading up to the meeting Monday, the administration has been reviewing conditions under which Russia, which still owns the compounds, could be permitted to reoccupy them. One option under consideration is stripping the premises of the diplomatic immunity they previously enjoyed.

Sebastian Gorka, a senior White House adviser to President Trump, told CNN on Friday that it was time for the U.S.-Russia relationship to “move on.” Trump, he said, pressed Russian President Vladi­mir Putin “on multiple occasions” about election tampering when they met last week at the Group of 20 summit in Hamburg.

“The president was not in a court of law,” Gorka said. “He pressed, he pressed the president of the Russian Federation, [and] the president of the Russian Federation denied” the allegations.

“We have to move on in the interest of U.S. national security and saving innocent lives,” he said.

In a tweet on Sunday, Trump said that “sanctions were not discussed” during his meeting with Putin. “Nothing will be done until the Ukrainian and Syrian problems are solved,” he tweeted. The United States and European partners maintain a set of economic sanctions against Russian persons and entities in response to Russia’s intervention in Ukraine, including the annexation of Crimea.

White House deputy press secretary Sarah Huckabee Sanders said that sanctions were discussed but indicated that the discussion was “specific to election meddling,” an apparent reference to the diplomatic expulsions and compound seizures.

Zakharova, the Russian Foreign Ministry spokeswoman, said that “the seized property has not been returned. Far from reversing the decision to expel our diplomats, Washington is refusing to issue visas to those who are supposed to replace them.”

A State Department spokesman, noting that visa adjudications are confidential, declined to respond.