Russian President Vladimir Putin on Saturday said it was “too early” to return the Ukrainian naval vessels and 24 sailors that Moscow captured last week, The Guardian reported.

Putin claimed his country had to detain them while it put together a legal case to show that the three Ukranian naval vessels violated Russia’s territorial waters in the Sea of Azov. Ukraine on Monday declared the imposition of martial law in its border regions for a month, a day after Russia seized three of its navy vessels off the Crimean Peninsula.

Ukraine said its soldiers were injured after a Russian border guard vessel allegedly rammed into one of its tugboats in the Kerch Strait, a narrow body of water that gives access to the Sea of Azov and is used by both nations. Russia had annexed the Crimean Peninsula in 2014. However, Russia claimed it had been forced to act as Ukrainian ships illegally entered its waters to “intentionally” provoke a conflict.

Speaking to reporters after the G20 summit in Buenos Aires, Putin claimed the three ships’ logs would show that they tried to cross the Kerch strait from the Black Sea into the Sea of Azov deliberately to provoke Russia.

Asked if he might consider exchanging the captive sailors for Russians in Ukrainian detention, Putin said: “We are not considering a swap and Ukraine did not raise this issue, and it’s too early to talk about that,” Putin said when asked if he would considering exchanging the sailors for Russians detained by Ukraine. “They are still being investigated. We need to establish the fact that this was a provocation by the Ukrainian government and we need to put all these things on paper.”

“The current Ukrainian leadership is not interested in resolving this at all,” Putin claimed. “As long as they stay in power, war will continue. Why? Because when you have provocations, such hostilities like what just happened in the Black Sea…you can always use war to justify your economic failures.”

Talks with foreign leaders

Putin also said that he spoke about the matter with several foreign leaders at the G-20 summit. United States President Donald Trump on Thursday cancelled an official meeting with Putin at the summit citing the Ukrainian crisis.

But the Russian president said he met Trump briefly on the sidelines of the summit. “I answered his questions,” Putin said, according to Bloomberg. “He has his position on these issues and problems. I have mine.” He also reportedly spoke to German Chancellor Angela Merkel and French President Emmanuel Macron. “I don’t know if I was able to convince them,” Putin said.