Moldova and Georgia have defended the quality of their wines in response to a Russian move to suspend imports on health and sanitation grounds.
Moldova and Georgia largely depend on Russia for wine sales
The head of Russia's consumer rights watchdog, Gennady Onishchenko, called this week for imports to be suspended.
As rail deliveries ground to a halt, Moldova sent a state delegation to Moscow to express its indignation.
Georgia invited Russian experts to test its wines at source while observers suggested the row was political.
Some believe it is another attempt by Russia to punish ex-Soviet states for severing ties with Moscow, the BBC's Chloe Arnold reports from Moscow.
Georgia's Western-leaning government has turned its back on Russia, and relations between Moldova and Moscow have soured over the breakaway, Russian-dominated region of Trans-Dniester.
Russia recently doubled the price Georgia and Moldova must pay for gas imports while subsidising energy supplies to countries like Belarus, which remain loyal to the Kremlin, our correspondent says.
Mr Onishchenko wrote to the Russian customs service asking it to stop wine imports from the two countries after tests this month "revealed a large share of samples of alcohol products and wine materials that do not meet safety requirements".
Traces of potentially dangerous pesticides had, he said, been discovered.
Our correspondent says that both Moldova and Georgia send as much as 80% of their wine exports to Russia and the ban could cripple the countries' economies.
Valeriu Mironescu, a member of the Moldovan delegation sent to Moscow, told Moldovan TV it was seeking to meet Russian officials to clarify what he called a "misunderstanding".
Georgia's agriculture ministry has said the Russian concerns are unfounded and it invited Moscow to attend laboratory tests on the spot.
Archil Gegenava, director of the Teliani Veli wine plant in Georgia, said some companies faced ruin.
"Russia accounts for 89% of Georgian [wine] exports," he told Georgia's Imedi TV channel.
"There are companies that sell 90 or even 100% of their wine to Russia - for them, this means ruin."