In televised remarks on Saturday, following a meeting with Ukrainian Prime Minister Yulia Tymoshenko in Moscow, Putin said Ukraine would have to invest considerable funds to retool its arms industry to produce weapons according to NATO standards.
Russia strongly opposes Ukraine's plans to join NATO, saying this move would jeopardize its security.
Ukraine's pro-Western leadership has been pursuing NATO membership since 2004, when President Viktor Yushchenko came to power. Ukraine failed to secure an agreement on a NATO Membership Action Plan (MAP), a key step toward joining the alliance, at the organization's summit in April, but was told the decision would be reviewed in December.
Meanwhile, Tymoshenko said that a decision on Ukraine's entry into NATO would only be made after a nationwide referendum.
Both parties also discussed the status of the Russian Black Sea Fleet currently stationed in Ukraine's Crimean port of Sevastopol.
The Russian Black Sea Fleet currently uses a range of naval facilities on Ukraine's Crimean peninsula under an agreement signed in 1997. Ukrainian President Viktor Yushchenko recently ruled not to extend lease terms for Russia's Navy beyond May 28, 2017.
Tymoshenko said Ukraine would fulfill its obligations under the lease agreement that allows the Russian Navy to stay in Sevastopol through 2017.
