"If it comes to a direct attack on the Russian Federation... then, of course, the question of the Russian Federation deploying all types of weapons at our country's disposal will inevitably and immediately be on the agenda. This is inevitable," Putin said at the annual Valdai forum.
In recent months, NATO countries have conducted several military exercises along the borders of Kaliningrad. That prompted Moscow to issue a statement condemning what it called "provocative statements and actions of the North Atlantic Alliance's leadership and NATO member states".
NATO in turn has denounced Russia's "threat of force, including any irresponsible nuclear rhetoric".
On Thursday, Putin once again condemned the "successive military exercises in the Baltic Sea" and the "attempts to intercept" Russian vessels.
"All this constitutes an escalation," he said.
"We have no intention of attacking anyone -- neither in 2029, nor in 2030, nor in 2050," Putin said.
"However, if we face aggression, we will be compelled to respond. Citizens of European countries need to clearly understand this," he added.