Black Sea subterfuge

The US claims that Russia is planning to attack civilian ships in the Black sea and claim that Ukraine's mines blew them up. Also that Russia has planted more mines.

Ukraine can legitimately retaliate against Putin's threats to attack civilian ships sailing to and from Ukraine, by attacking ships sailing to Russian ports. Especially the main Russian oil export port, Novorossiysk. To avoid polluting the shore, it should attack tankers traveling empty into Novorossiysk. To maintain better relations with other countries, it should attack Russian-owned or Russian-flagged ships, but not make a commitment to limit attacks to them.

This would do enormous economic harm to Russia, and I expect it would convince Putin to reestablish the Ukraine food export deal.

Of course, there may be reasonable things for Ukraine's supporters to do to facilitate export of food from Russia.