MOSCOW — Russia must develop new offensive weapons to counter US missile defences and prevent US policymakers from feeling they can "do whatever they want," Prime Minister Vladimir Putin said Tuesday.

"To preserve the balance, we must develop offensive weapons systems, not missile defence systems as the United States is doing," Putin said during a visit to the Russian Pacific port city of Vladivostok.

"The problems of missile defence and offensive arms are very closely linked," the powerful Russian prime minister said in comments broadcast on state television.

"By building such an umbrella over themselves our partners could feel themselves fully secure and will do whatever they want, which upsets the balance.

"Aggressiveness immediately increases in real politics and economics" in this situation, he added.

Putin's comments -- coming on the heels of a similar statement by President Dmitry Medvedev -- marked a toughening of Moscow's stance on strategic security ties with the United States.

The former Cold War foes are in talks on a successor to the now-expired START nuclear disarmament treaty.

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