The United States Congress shares foreign relations power with the president. The legislative and the executive branches both play important and different roles in initiating and changing foreign policy.
The president has the authority to initiate and implement foreign policy through making legislation proposals, negotiating foreign agreements, responding to foreign events and choosing foreign policy officials. The Congress has powers in finalizing trade agreements with foreign countries. The most ambiguous role of the Congress is to declare war. It also has the Power of The Purse, where it gives approval for funding and spending. The president holds the lead in foreign policy, but the Congress plays a central role.