(CNN)  -- The mayor of Ciudad Juarez, Mexico, is asking Mexican federal authorities not to pull military units out of the region for at least another six months. A Mexican soldier controls traffic at the Mexico-U.S. border customs post in Ciudad Juarez on August 16. A decision on whether to withdraw the troops is expected before September 15. The troops were sent to the city across from El Paso, Texas, in the spring of 2008 to help quell violence involving warring drug cartels. An additional surge of troops was sent this spring. That surge appeared to work at first, cutting the homicide rate in Juarez drastically. But murders in the city spiked over the summer.
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Mayor Jose Reyes Ferriz would like federal army troops to stay six more months
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Troops were sent to Ciudad Juarez to quell drug-fueled murders
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Murders down in spring, but spike in summer; more than 300 killed in August
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Decision on whether to withdraw the troops is expected before September 15
The mayor, @placeholder, attributed the summer spike in violence to wars between cartels over the control of street drug-sale points.