If the West is going to be aggressive with Russia, Putin made clear, then Russia is going to be aggressive with the West.
"If a new missile-defense system is deployed in Europe, then we need to warn you today that we will come with a response. We have to ensure our security, and we are not the initiators of this process," Putin said.
Putin's remarks -- a transcript of which has been published on the Kremlin website -- are the latest ultimatum in a mounting war of words with Washington over U.S. plans to base parts of a missile-defense shield in Poland and the Czech Republic.
U.S. President George W. Bush arrives today in Prague to discuss the plans with Czech officials.
The issue took on new urgency last week, when Russia successfully test-fired a new cruise missile and an intercontinental missile capable of carrying multiple warheads.
Russia defended the move as a response to the U.S. shield, and accused Washington of starting a new arms race.
"We relieve ourselves of the responsibility for any retaliatory steps, because it is not us who are initiators of the new arms race that is certainly imminent in Europe," Putin said in the interview on June 1.
"The strategic balance in the world is being upset. In order to restore this balance, without creating our own missile-defense system, we will be compelled to create a system to overpower this missile-defense system," he added.
Summit In Germany
Bush and Putin are due to discuss the issue on the sidelines of the G8 summit, which begins on June 6 in the German resort town of Heiligendamm.
They will also reconvene for talks in the Bush family's summer residence in Kennebunkport, Maine, on July 1-2.
Journalists did not limit their questions to the U.S. missile defense. They also raised the issue of Putin's plans once his second presidential term expires next year.
Putin has repeatedly said he will not seek constitutional changes that would allow him to win a third term in office.
In the interview with G8 journalists, however, the Russian president said he favored a change in the length of presidential terms from four years to five, six, or seven years. "Four years is certainly too short a term," Putin said.
This change would not affect Putin's current term, only those of his successors.
The Russian leader also discussed Britain's request to extradite Andrei Lugovoi, the Russian businessman and former KGB agent who has been named as the chief suspect in the poisoning death of Russian former security officer Aleksandr Litvinenko.
Putin dismissed the extradition request as "foolishness."
"If the people who sent us this demand do not know that, according to the Russian Constitution, Russian citizens cannot be extradited to foreign states, then their competence is in question," Putin said.