Banjul - Gambian opposition leader Adama Barrow said on Tuesday he believed his coalition would sweep the presidential election in two days time following unprecedented rallies nationwide, and urged President Yahya Jammeh to go peacefully if he loses power.The businessman emerged from obscurity to become the flagbearer of all The Gambia's opposition parties bar one after mass arrests of supporters from the largest anti-government grouping in April."People have shown us tremendous support. With that support we are 100% sure that we are going to win and with a big margin," he said on the final day of the two-week campaign.With no official opinion polls in The Gambia it is difficult to corroborate Barrow's claim, but diplomatic sources have indicated in recent days that Jammeh faces his most significant challenge since taking power in a 1994 coup.Jammeh has won four elections with his ruling Alliance for Patriotic Reorientation and Destruction, following a 2002 constitutional amendment lifting term limits."We believe in our support. If Jammeh wants advice, or, I'm giving him advice, if he loses, let him accept the will of the people and accept the value of the Gambian people," the opposition leader said.Barrow said a memorandum signed by all the coalition parties in October laid out plans for a reform-led administration.A third candidate, former ruling party deputy Mama Kandeh, is standing for the Gambia Democratic Congress.On Tuesday final rallies took place in Banjul, where campaigning has until now been overwhelmingly peaceful.More than 880 000 voters are expected to vote in this tiny west African nation on Thursday.