What did president kennedy imply that the united states would do to protect the people of west berlin?

He implied that they would use military force to defend them if necessary.

In his speech he explained that they are prepared to negotiate diplomatically should the Soviets try to take west Berlin to themselves which would go against their previous deal. He stated that they would also be prepared to use military force in case of being attacked and because of self-defense and would not allow them to break deals.