 By Walker's decision, provisional President Rivas summoned new elections on 10 March 1856, but countermanded the decree on 14 March, and broke relations with Walker.On 23 January 1857 Jerez formed a dual Junta government with the Conservative Tomás Martínez and they acted jointly as Presidents of Nicaragua, from 24 June 1857 to 19 October or 15 November 1857.In his subsequent career as Minister Plenipotentiary of Nicaragua to Costa Rica, he signed on 15 April 1858, the Cañas–Jerez Treaty that defined the boundaries between the two countries.