The only way for Russia to prevent grain ships from leaving ports in southern Ukraine is by missile strikes, said Indrek Kannik, head of the International Center for Defense and Security (ICDS) on Monday.
Grain shipments from Ukraine continued on Monday despite Russia's announcement over the weekend that it would withdraw from a United Nations-guaranteed grain transit agreement.
The Russian Navy has been pushed out of the western part of the Black Sea after the sinking of its flagship Moskva and abandoning Snake Island, Kannik said.
"For the Russians, the only real way to stop these ships would be to launch missile strikes against the grain ships. And that would be a step that the Russian leadership might not want to take at the moment," he told Monday's "Aktuaalne kaamera".
Security expert Rainer Saks said Russia is using attacks on Sevastopol in occupied Crimea as the reason to stop the exports.
"Russia is currently calculating whether it would be possible to carry out a blockade by force. This would mean blocking key trade corridors with warships. [But] Ukraine has shown that it can attack Russian ships," he said.
So far, the Kremlin has not interfered with grain transit but ship owners may not want to continue if guarantees are not given by all sides, Kannik added, saying this may prove to be the "biggest obstacle".
"Turkey and the UN, for their part, are putting a little pressure on Russia to show that they can continue with this activity. I suppose there is also some negotiation going on here as to whether it is possible to find some sort of solution that does not leave both sides with egg on their faces," said Kannik.
Editor: Helen Wright