BOGOTA (Reuters) - Two former Colombian presidents will back a joint right-wing ticket in elections next year, they said on Friday, focusing their platform on objections to the peace deal signed with the Marxist FARC rebels.

Ex-presidents Alvaro Uribe, who is now a senator with his Democratic Center party and Andres Pastrana, who leads the Conservatives, will jointly choose candidates for the presidency and vice-presidency, they said in a statement.

The two men have vehemently opposed the peace deal between the government of President Juan Manuel Santos, who will leave office in August 2018, and the Revolutionary Armed Forces of Colombia (FARC) rebels, who have demobilized and are now a political party.

“We will choose one candidate for the presidency and vice-presidency, from candidates chosen by the Democratic Center and the Conservative base led by Andres Pastrana, choosing the candidate with the best chance of winning the presidency,” the statement said.

The method for choosing between candidates has yet to be decided, it added.

Besides changes to the peace deal, which the two men say is not harsh enough on former rebels and does not require them to pay enough for crimes including murder, kidnapping and displacement, the coalition will focus on improvements to health care and the economy.

Uribe, who governed from 2002 and 2010 and managed a U.S.-backed offensive against the FARC, has yet to choose a candidate for his party. Pastrana, who himself attempted a peace process with the FARC during his 1998-2002 term, backs Conservative candidate Marta Lucia Ramirez, who also ran in 2014.

Corruption scandals, which have lately touched every major political party, are also expected to be a major theme in the 2018 race.

The country’s constitutional court has ruled the peace deal cannot be modified for the next 12 years.

Other presidential candidates for next year include former vice-president German Vargas Lleras, former government peace negotiator Humberto de la Calle, ex-governor Sergio Fajardo and former M-19 rebel and mayor of Bogota, Gustavo Petro.