TEGUCIGALPA, Jan 22 (Reuters) - The United States embassy in Honduras on Saturday called for calm and dialogue after lawmakers brawled in Congress a day earlier amid a dispute over who would head up the legislative body, just days before President-elect Xiomara Castro takes office. "Due to the events of January 21, the United States calls on political actors to remain calm, engage in dialogue and refrain from violence and provocative rhetoric, and urges their supporters to express themselves peacefully while respecting the rule of law," the U.S. embassy in Tegucigalpa tweeted. Castro"s legislative plans suffered a body blow on Friday when about 18 members of her Liberty and Refoundation Party (Libre) broke ranks and collaborated with the ruling National Party to elect a Libre lawmaker as the president of Congress. The dispute triggered chaotic scenes in Congress as the vote broke an agreement Castro had with Partido Salvador de Honduras (PSH), an allied party that helped her claim victory, to install a PSH figure as the Congress president. Castro, calling the move a "betrayal", expelled the 18 lawmakers from her party. She also called for Libre members from around the country to converge in the capital Tegucigalpa for a vigil to prevent Sunday"s election of a new board that would ratify Friday"s vote. read more Castro promised ally PSH leadership of Congress after its candidate, Salvador Nasralla, stepped down from the race and pledged support to Castro, the wife of former President Manuel Zelaya, who was ousted in a coup in 2009. Going against the deal with PSH will likely impact Castro"s ability to prevail in Congress, analysts say. Castro has threatened to refuse to be sworn in on Jan. 27 by the new president of Congress.