Right-wing Chilean President Augusto Pinochet made a rare plea for opposition support in his bid to rule until 1997, while the general's supporters and foes reportedly battled in the streets of a southern city. According to Radio Cooperative of Santiago, 10 people were injured when pro- and anti-Pinochet demonstrators clashed Wednesday in Valdivia, about 500 miles south of Santiago. Police arrested 30 of the demonstrators, the radio said, quoting a local youth leader of the opposition Christian Democratic Party. In a radio and television address Wednesday, Pinochet said he planned to forge a "new democracy" offering economic progress and legal safeguards against communism. (See news analysis story on A6.)