"The Ukrainian Foreign Ministry has sent a note to the Russian Foreign Ministry requesting an explanation for statements made recently by Russian politicians," a ministry spokesman said.
Lavrov said Tuesday Russia would do everything possible to prevent its neighbors, Ukraine and Georgia, being admitted to NATO.
"We will do everything possible to prevent the accession of Ukraine and Georgia to NATO and to avoid the possible worsening of relations with the alliance, its leading member states and our neighbors," he said in an interview with the Moscow-based Ekho Moskvy radio.
The Russian minister said Ukraine's and Georgia's possible admission is "the key irritant threatening to turn relations into a real problem with those NATO countries trying to force through this decision."
At a summit in Bucharest on Thursday, NATO members decided to postpone offering Georgia and Ukraine the chance to join the alliance's Membership Action Plan (MAP), but promised to review the decision in December. The ex-Soviet republics had received strong U.S. backing for their bids.
