United Nations Issues: Congressional Representatives to the U.N. General Assembly [Updated August 5, 2019] [open pdf - 418KB]
From the Document: "The annual session of the United Nations (U.N.) General Assembly is held at U.N. Headquarters in New York City. Generally, the President appoints one Democrat and one Republican to serve as U.S. representatives to the session, alternating each year between the House and Senate. At the 73rd session of the Assembly, which opened in September 2018, two Senators (Ron Johnson and Jeff Merkley) served as congressional representatives. Two members of the House will likely serve as representatives to the 74th Assembly session, which is scheduled to open on September 17, 2019."
CRS In Focus, IF10464
Congressional Research Service: https://crsreports.congress.gov/