Adding to the tensions was the Ukrainian parliament's decision this week to officially drop the neutrality the country adopted under Russian pressure in 2010.
The shift in Kiev's diplomatic allegiance was in line with Poroshenko's vow to put Ukraine under Western military protection in the face of Russian threats.
Ukraine sought NATO membership in the early post-Soviet era but was never viewed as a serious candidate.
The February change of regime in Kiev upset Putin's plans to get Ukraine to join a new bloc that Moscow hopes will counterbalance NATO and the European Union.
Moscow had also set Kiev's exclusion from all military unions as a condition for any Minsk deal.