Which US President used the phrase "Speak softly and carry a big stick"?

Big stick ideology, Big stick diplomacy, or Big stick policy refers to U.S. President Theodore Roosevelt’s foreign policy: "speak softly, and carry a big stick." Roosevelt described his style of foreign policy as "the exercise of intelligent forethought and of decisive action sufficiently far in advance of any likely crisis".

The idea of negotiating peacefully, simultaneously threatening with the "big stick", or the military, ties in heavily with the idea of Realpolitik, which implies a pursuit of political power that resembles Machiavellian ideals. It is comparable to gunboat diplomacy, as used in international politics by imperial powers.