By Julia Symmes Cobb
BOGOTA, July 20 (Reuters) - Colombian President Juan Manuel Santos opened a new session of Congress on Sunday, calling on lawmakers to back government efforts to strike a peace deal with Marxist rebels to end 50 years of war.
"This will be - there's no doubt - the Congress of peace," said Santos, who will be inaugurated for a second four-year term on Aug. 7.
"We have a great challenge - an achievable challenge - to end an armed conflict which has bled us for half a century, and build peace."
Santos won re-election last month with support for his bid to bring an end to five decades of war with the Revolutionary Armed Forces of Colombia, or FARC, that has killed more than 200,000 people and displaced millions.
Santos will face fierce opposition in Congress, not least from ex-President Alvaro Uribe, a newly minted senator and leader of the right-wing Democratic Center party. His backers won 20 percent of the Senate seats and just under 10 percent of the lower house in March elections.
Uribe is a staunch opponent of the peace talks, which he says will lead to impunity for FARC leaders and are a betrayal of the war's victims.
Talks have so far produced partial agreements on three topics - land reform, political participation and drug trafficking. Negotiators in Havana are now discussing reparations and justice for victims of the conflict.
The FARC and the smaller rebel group the National Liberation Army, or ELN, who are in preliminary talks with the government, released a joint statement urging lawmakers to support peace.
"Reconciliation is knocking at Colombia's door," the rebel statement said. "It's time to pass from rhetoric and dead words to a period of transition, when Congress will legislate in favor of the uniting of Colombian society."
The government will also seek congressional backing for reforms to taxation, pensions, healthcare and the justice system.
Members of Congress were sworn in during the ceremony in central Bogota.
Santos's governing coalition holds majorities in the lower house and Senate. (Additional reporting by Nelson Bocanegra)