Which country was not one of the Big Three Powers during the writing of the treaty that ended the war?

During the writing of the treaty that ended World War I, which was the Treaty of Versailles in 1919, Italy was not considered one of the Big Three Powers. The Big Three were the United States, the United Kingdom, and France. Although Italy was part of the Allies and participated in the negotiations, it held a lesser influence compared to the other three nations. Italy's expectations for territorial gains were largely unmet, leading to dissatisfaction with the treaty outcome.