When tensions flared up between Venezuela and Colombia in 2008, Russian President Vladimir Putin promised the late leader Hugo Chávez his support in case the South American neighbors went to war, the Washington Post said based on a new book by two Uruguayan journalists.

"You can count on my advice for whatever you need," Putin is reported to have told Chávez after the socialist leader, upset about a Colombian airstrike on a guerrilla camp in Ecuador, sent Venezuelan troops to the border.

"A Black Sheep in Power," a biography of former Uruguayan President José Mujica, has drawn much attention across Latin America for its purported revelations about Mujica's relationships with Chávez, former Brazilian President Luiz Ignácio "Lula" da Silva and Cuban leaders Raúl and Fidel Castro.

The book's authors, Andrés Danza and Ernesto Tulbovitz, stopped short of claiming that Putin assured Chávez military support in the case of war with Colombia. But the Russian president did recommend that the Venezuelan government make "the necessary purchases for a possible armed conflict," according to El Tiempo.

The border between Venezuela and Colombia is one of continent's busiest crossings and has been the cause of much friction between the South American neighbors, the Washington Post recalled. Two years after the 2008 incident, the relationship between Chávez and Colombia's then-President Alvaro Uribe once again soured to the point of the two nations briefly severing diplomatic ties.

Chávez ordered the Venezuelan Embassy in Bogotá closed on numerous occasions, while Uribe frequently accused Caracas of turning a blind eye to the presence of rebels from the leftist Revolutionary Armed Forces of Colombia (FARC) on Venezuelan territory, according to the newspaper.

Mujica and Chávez, meanwhile, had a close relationship and considered each other friends, though the Uruguayan leader voiced doubts about his Venezuelan counterpart's "socialist" ideology, Danza and Tulbovitz wrote in their biography, according to El Tiempo.

But "(Mujica) valued that Chávez brought many Venezuelans out of poverty," the journalists noted.

Chávez's successor, embattled President Nicolás Maduro, though, committed a mistake by trying to emulate his mentor's personality, Mujica judged, according to "Black Sheep."