GUATEMALA CITY, June 2 (Reuters) - Brazil will finance Guatemala's purchase of six military airplanes and a radar system to help it tackle a growing threat from drug gangs within its borders, Guatemalan President Alvaro Colom said on Tuesday.

Brazil's state-run export bank BNDES will fund the $99 million purchase with a 12-year loan, Colom told reporters in the Guatemalan capital during a visit by Brazilian President Luiz Inacio Lula da Silva.

The Super Tucano aircraft, made by Brazil's Embraer (EMBR3.SA: Quote, Profile, Research) (ERJ.N: Quote, Profile, Research), are due to be delivered within 18 months.

The turboprop airplane can be used in a variety of roles ranging from pilot training and airborne surveillance to ground attack, according to the Embraer website.

"The most important thing is that we'll have the same system as Colombia and Mexico so we can better coordinate the security of our borders," Colom told reporters.

Colom is cracking down on rampant police corruption and violent crime as the country battles increasingly well-armed and organized drug cartels moving across the border from Mexico.

He announced last week a $75 million anti-crime initiative that aims to clean up police forces and improve crime-fighting. The impoverished nation is seeking aid from foreign governments to help pay for the program.

An average of 17 people are murdered every day in Guatemala, a country of only 13 million which is one of the most violent in Latin America. A United Nations backed commission estimates that 98 percent of crimes go unpunished. (Reporting by Sarah Grainger; editing by Mohammad Zargham)