(CNN) -- Colombia's Constitutional Court on Tuesday ruled that a military agreement that would give U.S. troops access to seven Colombian military bases is unconstitutional.

The agreement has been a source of tension between Colombia and neighboring Venezuela.

The court said that the agreement must be sent to the Colombian Congress for approval before it can become effective.

The court ruled that the agreement over use of the bases was not an extension of treaties signed between the two nations in the past, but a new treaty that requires the approval of the legislature to be valid.

"It's certainly a big bump in the road, but it's not a huge setback," Adam Isacson, senior associate at the Washington Office on Latin America organization told CNN.

The congressional make-up is about 80 percent backers of current president Juan Manuel Santos and former President Alvaro Uribe, who was in office when the agreement was signed, Isacson said. So congressional approval could come quickly.

But there is also the possibility that it could drag for a year, he said.

Because the military bases agreement had not yet been implemented, there would be no major changes on the ground, Isacson said, adding that under previous agreements, the United States already has some troops in Colombia who will continue to operate under those previous treaties.

The United States says it needs to operate on the bases to help in its fight against terrorists and narcotraffickers, especially since the closure a few months ago of a U.S. base in Ecuador. The United States maintains similar "forward operating locations" in El Salvador and Aruba-Curacao.

Colombia's agreement to host the Americans has come under criticism in Latin America, particularly from President Hugo Chavez in Venezuela.

In the past, Chavez has likened the agreement to an act of war and accused the United States of wanting to stage military personnel nearby to destabilize his leftist government. More recently, he has said that Colombia has the right to pursue an agreement if it wants.

CNN's Mariano Castillo contributed to this report.