A feared hard Left guerrilla group operating in the mountains that border Venezuela and Colombia has vowed to respond to any military intervention by the US to topple Nicolas Maduro.

In a rare interview from temporary exile in Cuba, leaders of Colombia's National Liberation Army (ELN) told the Sunday Telegraph they were drawing up a strategy to help Venezuela repel a possible invasion.

The Marxist group's comments demonstrates the prospects of a messy and protracted conflict if the US chooses to use force against Mr Maduro, the Venezuelan president. Mr Maduro warned Donald Trump this week that the US president was walking into his own Vietnam.

John Bolton, the US national security adviser insisted this week that "all options are on the table" after he was pictured holding a notepad ahead of a briefing on the Venezuela crisis that said "5,000 troops to Colombia".

The ELN have been blamed for a wave of terror attacks in Colombia where they filled a power vacuum left by the Farc when a peace deal brought the world's longest running civil conflict to a close.