SEOUL, South Korea -- South Korea has reached an agreement with the United States that lets Seoul more than double the range of its ballistic missiles to counter what it considers to be a growing threat from North Korea.

The revised agreement, which also tries to address Washington's worries about a regional arms race, increases the payload the ballistic missiles can carry and allows South Korea to develop and deploy more powerful unmanned aerial vehicles, or drones, that can carry more reconnaissance equipment and weapons.

Under the revised guidelines, South Korea can deploy ballistic missiles with a range of up to 500 miles, enough to reach any target in North Korea but not enough to be considered a threat to China or Japan, as long as the payload does not exceed 500 kilograms (about half a ton). Seoul can also load warheads weighing up to 2 tons on ballistic missiles with shorter ranges.

Until now, South Korea has been barred from deploying ballistic missiles with a range of more than 187 miles and a payload of more than 500 kilograms. -- a capacity Korean officials believed was not enough to protect their country from North Korea's rapidly expanding nuclear and missile capabilities. The South was also barred from deploying drones that can carry more than half a ton of weapons or equipment.

The new agreement allows South Korea to use drones that can carry up to 2.5 tons of equipment and weapons.

"The biggest objective for the revision is to prevent North Korea's military provocations," said Chun Yung-woo, the chief national security adviser for President Lee Myung-bak.