(Adds comment from officials in New Mexico)
By Roberta Rampton
WASHINGTON, May 21 (Reuters) - President Barack Obama on Wednesday declared almost 500,000 acres (202,000 hectares) of mountains, canyons and desert caves near the U.S.-Mexico border a national monument, which drew criticism from Republicans and local law enforcement that the move could put border security at risk.
The Organ Mountains-Desert Peaks region includes "Outlaw Rock" where Billy the Kid inscribed his name more than 130 years ago, and Apache chief Geronimo is believed to have used the mountains to hide out.
Obama, who is extolling the economic benefits of tourism this week, took a 10-minute stroll over to the Interior Department from the White House to sign the proclamation, greeting tourists from Israel, China, Germany and elsewhere who were walking on the National Mall.
Obama said the designation could double visitors to the region and boost the local economy by more than 70 percent.
"Anyone who's ever seen the Organ Mountains that overlook Las Cruces, New Mexico, will tell you that they are a spectacular sight," Obama said.
"You got massive rocks that jut up 9,000 feet (2,740 meters)in the air and stretch for 20 miles (32 km), like the organ pipes of a giant," he said.
The administration said the designation had the backing of local business people, ranchers, tribal leaders and others in the region.
But Republican Representative Steve Pearce called the move a "land grab" that could hurt security in the region and House Republican Speaker John Boehner said the monument could hurt border security.
But a spokeswoman for U.S. Customs and Border Protection said in a statement that the designation would "in no way limit our ability to perform our important border security mission."
Dona Ana County Sheriff Todd Garrison also took issue with the president's action, saying that it would complicate law enforcement efforts in the area.
"It's hard for me to see the positives of this," Garrison said. "It is not an issue the president should have signed off on without conferring with local law enforcement."
But Dona Ana County Commissioner Billy Garrett disagreed, saying that the designation had been a decade in the making and was critical to preserving the heritage of the area.
"The (Bureau of Land Management) will develop a management plan with public input and that will include the needs of law enforcement," he said.
(Additional reporting by Joseph Kolb in New Mexico; Editing by Eric Walsh and Lisa Shumaker)