Ukrainian President Petro Poroshenko gave an interview to Germany’s Bild newspaper on Thursday in which he urged NATO to deploy warships in the Sea of Azov to forestall a possible Russian invasion of his country.

“Germany is one of our closest allies and we hope that states within Nato are now ready to relocate naval ships to the Sea of Azov in order to assist Ukraine and provide security,” Poroshenko said.

“We cannot accept this aggressive policy of Russia. First it was Crimea, then eastern Ukraine, now he wants the Sea of Azov. Germany, too, has to ask itself: What will Putin do next if we do not stop him?” he added, describing Russian President Vladimir Putin as an aspiring “emperor.”

“We had to react after this act of aggression, and therefore I imposed martial law in some regions, because we have to protect our country. It’s like in 2014. Putin wants to annex another part of Ukraine, he’s behaving the same way,” Poroshenko warned, alluding to Russia’s 2014 annexation of Crimea.

The BBC found it unlikely that NATO would deploy warships to the Sea of Azov, which is connected to the Black Sea via the Kerch Strait, a strategically vital passage that was the scene of Sunday’s attack on Ukrainian ships by Russian forces.

One of the sticking points is the very treaty Ukraine accuses Russia of violating, and vice versa: a 2003 bilateral agreement that gives them joint control over the Sea of Azov. Under this treaty, Russia and Ukraine would both have to grant permission for NATO warships to sail through the Kerch Strait. The Russians are already prone to complaining about NATO buildups along their borders and would likely object to even the boost of Black Sea naval deployments suggested by the BBC.

Russian President Vladimir Putin appears to be in no mood for indulging Poroshenko’s plea for peacekeepers. At a business forum in Moscow on Wednesday, Putin complained that the West indulges Ukraine too much and would allow Kiev to “get away with anything,” up to and including cannibalism.

“If they demand babies for breakfast, they would probably be served babies,” Putin said of the Ukrainians. “[The West] would say, ‘Why not? They are hungry. What is to be done about it?’”

“This is such a shortsighted policy and it cannot have a good outcome. It makes the Ukrainian leadership complacent, gives them no incentive to do normal political work in their country or pursue a normal economic policy,” he charged.

The Ukrainian border security service announced on Thursday that for the duration of martial law, expected to last for at least 30 days, only Ukrainian citizens will be allowed to travel to the Russian-annexed Crimean peninsula.

Radio Free Europe noted these restrictions are only slightly more onerous than Ukraine’s normal approach to Crimean travel since the Russian occupation:

“In connection with the introduction of martial law, the administrative border with temporarily occupied Crimea can be crossed exclusively with Ukrainian documents,” a spokesman said on November 29.

Citizens from all nations were previously allowed to enter Crimea through the administrative border via mainland Ukraine. But the process for doing so for non-Ukrainians was fraught with bureaucracy.

Crimea is accessible by plane from Russia or via Russia’s newly built bridge from the country’s mainland. But under Ukrainian law, those routes are illegal. Violators — and there have been many — are given official bans of three years or longer by Kyiv.

The Kremlin on Wednesday denied Ukrainian complaints that 35 of its merchant ships have been denied passage through the Kerch Strait, leaving half of them stuck in the Sea of Azov and the other half parked in the Black Sea. Kremlin spokesman Dmitry Peskov insisted traffic is flowing normally through the strait and suggested the Ukrainian ships ran afoul of bad weather.

Ukraine’s SBU intelligence agency on Thursday claimed a Russian Ka-52 helicopter and Su-30 jet fighter launched rockets at the Ukrainian ships seized by Russia in Sunday’s confrontation. “It’s a miracle the Ukrainian seamen have survived,” SBU deputy chief Oleh Frolov said.