Uribe re-election effort hits snag in Colombia

* Nonbinding arbiter ruling goes against re-election push

* Constitutional Court has last word on referendum

* Uribe seen as Washington's free-market ally in the Andes

By Hugh Bronstein

BOGOTA, Nov 13 (Reuters) - A bid to elect Colombian President Alvaro Uribe to a third term next year hit a snag on Friday after a panel of arbiters ruled that signatures collected in support of the effort were gathered improperly.

Opponents of a constitutional amendment to allow Uribe to run again said the decision by the National Electoral Council arbiters kills his chances of standing in the May election.

But re-election supporters say the arbiters exceeded their jurisdiction in ruling that Uribe campaign workers spent more money than allowed to collect about four million signatures supporting the change in law.

The final decision falls to the Constitutional Court, which is reviewing a bill passed by Congress calling for a referendum on the proposed constitutional amendment.

The court's nine judges are to take the arbiters' ruling into consideration when they issue their decision, expected early next year, to uphold or strike down the referendum bill.

If the Constitutional Court upholds the measure, Uribe's supporters will face a tight schedule for getting the referendum passed in time for him to run in May.

Colombian law was already changed once to let him stand for re-election in 2006. Those opposed to another term say it would throw off he country's democratic balance of powers.

Uribe has not said if he wants to run again. But his government has lobbied hard for the referendum and he insists that his security and investment policies should continue after his current term ends in August 2010.

The president, whose popularity stands at 64 percent, is seen as a hero by many voters and investors for his U.S.-backed crackdown on drug-running Marxist rebels widely despised for their practice of kidnapping.

He is Washington's main ally in the Andean region and considered a market-friendly buffer against left-wing revolutionary governments in Venezuela and Ecuador. (Reporting by Hugh Bronstein, editing by Vicki Allen)