The reversal dampened hopes for an imminent end to decades of violence that have continued to plague the South American country despite a 2016 peace pact that led to the disarmament of the FARC guerrilla group.

Colombian President Gustavo Petro had declared on New Year's Eve that a temporary truce had been agreed with the country's five largest armed groups, including the National Liberation Army (ELN), from January 1 to June 30.

The government subsequently said the ceasefire, hailed by the international community, would be monitored by the United Nations, Colombia's human rights ombudsman and the Catholic Church.

UN Secretary-General Antonio Guterres said it "brings renewed hope for comprehensive peace to the Colombian people as the New Year dawns."

But then on Tuesday, the ELN said it had "not discussed any bilateral ceasefire with the Gustavo Petro government, therefore no such agreement exists."

The group added that "a unilateral government decree cannot be accepted as an agreement."

This prompted the government Tuesday to concede that a proposed ceasefire decree had not yet been finally signed.

And on Wednesday, Interior Minister Alfonso Prada told reporters in Bogota that "we have decided to suspend the legal effects of the decree" in view of the ELN's stated position.- 'Total peace' -

Negotiations between the government and the ELN, the country's last recognized rebel group, have been under way since November.

A first round of peace talks since Petro came to power in August as Colombia's first-ever leftist president, concluded in Caracas, Venezuela on December 12 without a truce being agreed.

Another round of talks is due to take place in Mexico, although no date has been set.

Prada said the issue of a ceasefire will be taken up again in Mexico.

Tuesday's ELN statement said the group was "ready to discuss the proposal for a bilateral ceasefire."

In pursuit of Petro's quest to bring "total peace" to Colombia, the government is offering armed groups "benevolent treatment from the judicial point of view," Senator Ivan Cepeda recently told AFP.

This would be in exchange for "a surrender of assets, a dismantling of these organizations" and agreeing to stop their "illicit economies."

According to Petro's tweet, the government had "agreed to a bilateral ceasefire" with the ELN, two dissident splinter factions of the disbanded FARC, the Gulf Clan narco group and the Self-Defense Forces of the Sierra Nevada, a rightwing paramilitary organization.

The ELN is the only group to have refuted the announcement by Petro, who was himself an urban guerrilla member in his youth.

- Over 50 years of violence -

Negotiations between the government and armed groups which have an estimated combined total of 15,000 fighters, have so far failed to end the spiral of violence engulfing the country.

Colombia has suffered more than 50 years of armed conflict between the state and various groups of left-wing guerrillas, right-wing paramilitaries and drug traffickers.

The Indepaz research institute recorded nearly 100 massacres in Colombia last year.

Despite the peace agreement that saw FARC guerrillas disarm in 2017, armed groups remain locked in deadly disputes over drug trafficking revenues and other illegal businesses, according to the think tank.

Colombia is the world's largest cocaine producer.

The ELN, created in 1964, had announced a unilateral ceasefire from Christmas Eve to January 2.

Official estimates are that some 3,500 ELN fighters are present in 22 of Colombia's 32 departments.