The Ukrainian vessels - a tug and two gunboats - were trying to pass through the Kerch Strait from the Black Sea to the Sea of Azov, but were refused access and chased into global waters by 10 Russian vessels.
On Wednesday, Poroshenko donned camouflage utilities to tour a military training center and warned that Russia is building up forces in the eastern Ukraine region controlled by Russian-backed separatists.
Russia said the Ukrainian ships illegally crossed into Russian waters and called the crisis a "planned provocation".
Amid speculation that Poroshenko would use martial law as a pretext to postpone a spring 2019 election in which polls show he faces an uphill battle to win a second term, the parliament speaker signed a resolution setting the date for March 31. Mr. Trump, in an interview with The Washington Post on Tuesday, said he may cancel the sit-down with Putin in Argentina following Russia's seizure of three Ukrainian naval ships last weekend. "The current president immediately provokes the imposition of martial law, and this means only one thing - this means that the incident itself was provoked to impose martial law".
Just days after a major clash between Russia and Ukraine, the Russian military has announced plans to send more S-400 surface-to-air missile systems into Crimea. Ukraine insists they are prisoners of war, says some were seriously injured in the confrontation and has asked the International Red Cross to arrange a visit to see them.
Trump has been briefed on the situation as he considers whether to cancel the Putin meeting but no decision has been made, White House officials said on Wednesday.
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Over the weekend, violent clashes occurred as the United States attempted to stem the flow of people crossing into the country. Like other federal law enforcement officers, Border Patrol agents are allowed to use force if they think they are under attack.
A court in Crimea's capital Simferopol on Wednesday ordered nine of the 24 captured Ukrainian sailors - including senior Ukrainian naval officers and at least one member of Ukraine's SBU intelligence agency - held for a period of two months.
"This is no way for a law-abiding civilized nation to act", Haley said at a Monday emergency meeting of the U.N. Security Council.
Western governments have rallied behind Kiev, accusing Russian Federation of illegally blocking access to the Sea of Azov, used by both countries, and of using force without justification. "This can be the best guarantee for the security of this area from Russian aggression", says Parubiy.
"I hope they understand that", he said.
Volker said he has not received independent USA verification of Ukraine's information, but believed "the data the Ukrainians have provided is quite clear".
Meanwhile, U.S. State Department spokeswoman Heather Nauert urged European states to do more to support Ukraine and said Washington wants to see tougher enforcement of sanctions against Russian Federation.