Russia’s Foreign Ministry has issued a statement today warning that they believe there are too many US spies operating in Moscow under diplomatic cover, and that they may decide to expel some of those “diplomats” soon in retaliation for US moves late last year.

Those US moves included the expulsion of 35 Russian diplomatic personnel, including consulate cooks, and the seizure of a pair of vacation houses belonging to the Russian government as diplomatic compounds, which the US took as part of sanctions for “election hacking” allegations.

Russia was very public in deferring the retaliations until after President Trump took office, expecting the Trump Administration to return the seized facilities. That hasn’t happened, however, and patience is wearing thing, with Russia’s diplomatic corps wanting to do something in retaliation.

The Foreign Ministry statement held out hopes that the US could reverse its sanctions and resolve the whole situation, but warned that time is running out, and that they’ll soon feel obliged to retaliate, expelling some US diplomats.

The spy allegations are almost certainly true, as large nations commonly use their diplomatic facilities as a way to get spies into the country as employees, which also gives them diplomatic immunity if caught. The US made the same charges of the Russians in their expulsion last year.

The big question is not if the US has spies in Russia working at the embassy, but rather how effectively Russia could identify them for the sake of this expulsion. If they expel the wrong people, it’s tantamount to admitting they haven’t identified the right ones, and such a revelation is a big part of why nations rarely make such expulsions.