Who has the responsibility to negotiate agreements between United States and their host country-?

The United States Department of State, led by the Secretary of State, is primarily responsible for negotiating agreements between the United States and other countries, including host countries where the U.S. has diplomatic relations or conducts operations. The State Department, through its diplomatic missions and negotiators, engages in bilateral or multilateral negotiations with foreign governments to establish treaties, agreements, and memorandums of understanding that govern economic cooperation, trade, military alliances, cultural exchange, development assistance, and various other areas of international relations.