By Marc Frank and Daniel Trotta
HAVANA/BOGOTA (Reuters) - Colombia pledged on Sunday to de-escalate military action against leftist guerrillas if the rebels uphold their unilateral ceasefire, providing a breakthrough in peace talks that had been threatened by an escalation of battlefield violence.
President Juan Manuel Santos said he would analyze the situation in four months to decide if talks with the Revolutionary Armed Forces of Colombia (FARC) would continue.
In a joint statement with FARC rebels in Havana, the Colombian government said it would enact "de-escalation of military actions" beginning July 20 as long as the FARC maintains a ceasefire it called for that date.
Santos called the announcement "an important step to advancing toward agreement."
The two sides have been engaged in peace talks in Cuba for 2-1/2 years in an attempt to end Latin America's longest war, which has killed some 220,000 people and displaced millions over 50 years.
But the talks have been overshadowed by an increase in fighting this year.
Santos has said he would like to reach a peace agreement in 2015, and the two sides pledged on Sunday to work "without delay" toward a deal.
"We will be vigilant about what has been agreed today," Santos said in a televised address. "In four months from now, depending on how the FARC meet (the agreement), I will take the decision of whether to continue with the process or not."
To accelerate talks, they agreed to alter the structure, putting all remaining issues on the table at once instead of adhering to one topic at a time.
With the peace process in peril, the FARC on Wednesday called a unilateral ceasefire starting July 20, the sixth such ceasefire it has called during the course of the talks.
The FARC has long advocated a bilateral ceasefire, which the government has rejected saying the group has used previous attempts at such truces to rearm.
However, amid concerns that talks were floundering, media in Colombia began speculating Santos might soften his stance.
Santos has to balance his desire for peace with skepticism from right-wing opponents back home, who mistrust the FARC and accuse Santos of going soft after his predecessor, Alvaro Uribe, had weakened the rebels with a military offensive.
The government emphasized that de-escalation was not tantamount to a government ceasefire, and that the armed forces would respond based on FARC actions.
(Additional reporting by Helen Murphy; Writing by Daniel Trotta; Editing by Jeffrey Benkoe and Eric Walsh)