FILE PHOTO: Juan Guaido, President of the Venezuelan National Assembly and lawmaker of the opposition party Popular Will (Voluntad Popular), greets supporters during a gathering in La Guaira, Venezuela January 13, 2019. REUTERS/Carlos Garcia Rawlins/File Photo

CARACAS (Reuters) - Venezuelan opposition leader Juan Guaido took an oath swearing himself in as the South American country’s interim president on Wednesday, as hundreds of thousands marched to demand the end of socialist President Nicolas Maduro’s government.

Guaido, the head of the opposition-run Congress, has said he would be willing to assume the presidency on an interim basis with the support of the armed forces to call elections. The United States is mulling recognizing him as the country’s legitimate president, sources said.