(Adds comment from Uribe, details, paragraphs 1, 5, 7-8)
BOGOTA, Aug 6 (Reuters) - A Colombian high court ruled on Wednesday that Marxist rebels found guilty of atrocious war crimes cannot hold public office, a decision that may block some FARC leaders from entering politics and complicate negotiations to end five decades of war.
The ruling by the constitutional court throws into doubt agreements reached between the government and leaders of the Revolutionary Armed Forces of Colombia (FARC) that laid the groundwork for rebel political participation if the two sides agree on peace terms.
President Juan Manuel Santos will be sworn in to office on Thursday after winning a second term, mostly on the back of his bid to end the conflict that has killed more than 200,000 people and displaced millions.
Santos launched peace talks with the FARC at the end of 2012 with massive popular backing, but months of negotiations amid ongoing war and continued rebel attacks against civilian targets have dimmed support and left many questioning if the guerrillas should be allowed to hold office.
The court ruled that only rebels who have been involved in lesser crimes can seek election to political office. The interpretation of what constitutes atrocious crimes and lesser crimes will be decided by Congress, Luis Ernesto Vargas, president of the court, told reporters.
The decision may please some critics of the peace talks, most notably former president Alvaro Uribe, who has expressed outrage that FARC crimes could go unpunished and that rebel commanders may end up with seats in Congress.
"Even if crimes against humanity and genocide prevent participation, it's too bad other serious crimes make them eligible," Uribe, whose father was killed in a FARC kidnapping, said on his Twitter account.
Many FARC leaders face charges ranging from murder to kidnapping, torture, sexual violence, forced disappearances and recruitment of children. The government could try to offer alternative sentences that would later allow participation.
The FARC has not yet responded publicly to the court ruling, but has previously rejected the idea of serving any jail time.
FARC political participation is one item on a five-point agenda that the two sides have already agreed. The details of the accord have not been made public.
They have also agreed on terms of land reform and how to end the illegal drug trade. Still to be discussed is the complex issue of reparation to victims and how to end the conflict. (Reporting by Helen Murphy and Luis Jaime Acosta; Editing by Lisa Shumaker and Paul Tait)