The United States has asked Colombia to take "appropriate steps" to sustain relations a day after a key bilateral military accord was declared unconstitutional.

A Colombian constitutional court on Tuesday ruled the accord was unconstitutional because it had not received approval from the Colombian congress.

The agreement gives US military access to seven Colombian bases, a move that does not sit well with neighbouring Venezuela which has firmly opposed the 2009 accord as a threat to its government.

On Wednesday Philip Crowley, a US state department spokesman, said the US looks "to the Santos government to take appropriate steps to make sure that we can sustain our bilateral relationship".

"There can be, you know, actions taken by the executive or by the legislative branch to overcome, you know, the questions that have been raised," Crowley said.

Military pact

The US has sought to allay Latin American concerns about the military pact by insisting that it is not aimed at third countries.

The agreement, it says, which limits the number of US military personnel in Colombia to 800 and the number of US civilian contractors to 600, is aimed at fostering bilateral cooperation against drug trafficking, illegal armed groups and terrorism.

Charles Luoma-Overstreet, another US state department official, told AFP that the close US-Colombian defence cooperation will continue under previously existing agreements.

The US has provided Colombia, its most important ally in South America, more than $6bn in aid over the past decade to combat drug trafficking and leftist guerrillas under a programme known as Plan Colombia.

At the end of last year, the US congress approved 46 million dollars to refurbish Colombia's Palanquero base, one of the seven included under the agreement.

But congress made it clear it was not authorising the establishment of a permanent US base on Colombian territory.