German Chancellor Angela Merkel has stressed there is “no military solution”, after Ukraine’s leader urged Nato to send ships to the Sea of Azov.
Petro Poroshenko’s request came following a naval confrontation with Russia in waters off Crimea.
On Sunday, Russia opened fire on three Ukrainian ships and seized their crews in the Kerch Strait.
Mrs Merkel said the crisis was “entirely the doing of the Russian president”.
However, she said that “issues like these can only be solved by sensible dialogue”.
Russian President Vladimir Putin accused Mr Poroshenko of creating the naval “provocation” to boost his ratings ahead of 2019 elections.
President Poroshenko has implemented martial law across Ukraine’s border regions for 30 days in response to the crisis.
Meanwhile, Russian state media report that Moscow has delivered a battalion of S-400 surface-to-air missiles to north Crimea, and also plans to build a new missile early-warning radar station there.