The answer is:
 working with other governments to oppose the regime 
calling for transition to democracy 
imposing sanctions 
recognizing opposition groups 
providing humanitarian aid
According to what the president said to the public, the main goal of United States wanted to intervene with the situation in Syria is because it wanted to make the country as our ally. Opposing the government regiment and providing helps for the damage that the regimen caused is part of the necessary steps that it felt needed to achieve the goal.