Colombia's Santos opts for diplomacy in Uribe, Maduro spat By Helen Murphy BOGOTA (Reuters) - Colombian President Juan Manuel Santos on Monday refused to be drawn into a war of words between his predecessor - and harshest critic - and Venezuela's new president, Nicholas Maduro. Maduro, elected last month to replace the late Hugo Chavez, said on Friday he had evidence that Alvaro Uribe, president of Colombia from 2002 until mid 2010, was conspiring with the Venezuelan opposition to kill him. Santos was reprimanded on social media and by another former president for not responding to Maduro's explosive comments, which also included an allegation that Uribe could have been involved in the death of a Venezuelan journalist. Santos said he would not comment publicly on the dispute - a veiled poke at Uribe, who has used his Twitter account to defend himself against Maduro's attacks that he is a "Mafioso" and "murderer." "The dignity of former presidents is defended better - not with shouts or public insults - but through the corresponding diplomatic channels," Santos said on his Twitter account. While Santos is playing it safe, Maduro's outburst against the former head of state threatens to disrupt the diplomatic peace between the two nations, formed by Chavez and Santos after years of cross-border bickering. Caracas broke off diplomatic relations with Uribe's government in 2010 after he accused the leftist Chavez of harboring FARC rebel leaders inside Venezuela. Santos, who has frequently sparred in public with Uribe, was chided by former President Andres Pastrana for not responding to Maduro's comments. "What's at stake is Colombia's dignity," said Pastrana, who held office before Uribe. We can't let a former president be insulted because there are discrepancies between Santos and Uribe. For many Colombians, it was not surprising that Santos did not jump to defend Uribe, his former boss when he served as defense minister, since the two have been at loggerheads for the best part of his presidency. A conservative and staunch U.S. ally, Uribe has been Santos' fiercest and most public critic, most rabidly against his ties with Caracas and his bid to reach a peace accord with the Revolutionary Armed Forces of Colombia. Maduro, the self-professed "son of Chavez," has made a series of accusations since taking office last month. He has accused the United States of seeking to kill opposition leader Henrique Capriles to stir chaos and spark a coup. He later said he himself was the target of an assassination plot by mercenaries from El Salvador. Uribe on Sunday urged Colombia's attorney general to investigate Maduro over the "irresponsible slanders and threats," in case the Venezuelan leader ever visits Colombia.