By Wayne Cole SYDNEY (Reuters) - Uncertainty gripped Asian markets on Tuesday as investors braced for a potentially pivotal U.S. presidential debate, shunning stocks while favoring safe-haven bonds and the yen. Early jitters saw Japan's Nikkei sink 1.4 percent to its lowest in seven weeks, while the dollar dropped to a one-month trough around 100.08 yen before steadying. A higher yen is seen as a threat to exporter sales and profits.

By Helen Murphy and Luis Jaime Acosta CARTAGENA, Colombia (Reuters) - Colombia's center-right government and the Marxist FARC rebel group signed a peace deal on Monday to end a half-century war that killed a quarter of a million people and once took the Andean country to the brink of collapse. After four years of peace talks in Cuba, President Juan Manuel Santos, 65, and rebel leader Timochenko - the nom de guerre for 57-year-old Rodrigo Londono - warmly shook hands on Colombian soil for the first time and signed the accord with a pen made from a bullet casing. A crowd of dignitaries chanted: "Long live Colombia, long live peace" as Santos handed Timochenko a white dove pin.