SACRAMENTO - California's off-road riders have launched an aggressive campaign to oppose any move by the Marines to annex Johnson Valley, a nationally acclaimed high-desert recreation area on the perimeter of an important military base at Twentynine Palms.The potential expansion of the battlefield training ground for troops being deployed to Iraq and Afghanistan has sparked a conflict between the traditionally conservative off-road community and the military.It also may pressure Rep. Duncan Hunter, R-Alpine, a former Army Ranger and outspoken advocate for the military, to choose between his loyalties to the Marine Corps and to longtime off-road allies alarmed over shrinking legal places to ride."We're pretty devastated," said Ed Stovin, president of the San Diego Off-Road Coalition. "It's hard to fight national security when you're at war, but you sure hate to lose the area."Stovin said he hopes the off-road community can work with Hunter on a compromise, perhaps pushing the Marines to consider taking land not used for off-roading. "He's a good friend of ours," Stovin said.Hunter has not taken sides, said Joe Kasper, a spokesman. "Congressman Hunter supports both the interests of the off-roading community and the potential expansion of the facility to better simulate and prepare our Marines for conditions in Iraq and Afghanistan," Kasper said.Hunter plans to address the issue at a meeting with off-road enthusiasts March 22.Off-roading is a booming sport, with nearly 1 million vehicles registered in California to take to the terrain. About 4 million people ride in state parks set aside for that use, and countless others use federal land.Off-road advocates say they are squeezed for space by urban demand and environmental-based restrictions.Growing more alarmed as word spread of the possible land requisition by the Marines, off-roaders this week mounted a four-hour "virtual rally" over the Internet in a show of solidarity. By their count, there were 1,495 messages posted and 33,976 page views within four hours.Many posts carried a common theme: admiration for troops, hopes that they return home safely and support for the military - but near-unanimous opposition to turning the valley over to the Marines."The Marine Corps has a need, but the off-road community also has needs and rights to enjoy and recreate in this well-established off-highway vehicle area," Philip Hall of National City wrote."If this land were unused and dormant, it would be a different situation all together," Hall's post continued. "But Johnson Valley OHV area already has a purpose and is owned by thousands of tax-paying citizens like myself who are not willing to sacrifice such a pristine locale to be turned into a practice war ground."The Marine Corps has issued a statement confirming that it is looking to expand training facilities, but it says no decision has been reached and urges patience."This process of simply figuring out what land the base might actually need to meet the Marine Corps training requirements and how it affects other interests could take anywhere from three to five years," said Jim Ricker, assistant chief of staff at the Twentynine Palms base.The statement continued: "It is imperative that the Marines receive the most realistic training before deploying into a combat environment that demands split second life or death decisions."The 140,000-acre off-highway vehicle area, located southeast of Barstow in San Bernardino County, also is home to the federally protected desert tortoise, a fact that could provoke strident opposition from environmentalists.Protecting the tortoise was a key issue when the Army expanded training facilities near Fort Irwin a few years ago.Johnson Valley is under the supervision of the U.S. Bureau of Land Management. Mike Pool, California's BLM director, is expected to attend Hunter's March 22 meeting with off-road enthusiasts.John Dearing, a BLM spokesman, said the military followed a regular process before taking other federal lands."We have not yet received an application from the Marines," said Dearing, referring specific questions about Johnson Valley to the military.The Marine Corps said it plans to prepare an environmental review of alternatives once a decision is made. It promises full disclosure and public participation.Johnson Valley is nationally known as "the Hammers" - one of the best four-wheeling, boulder-hopping areas in the country, off-roaders say.The off-roading mecca draws thousands every year to numerous organized events, including rock-racing, rock-crawling and a "King of the Hammers" championship each February. The area's landscape is dotted with Joshua trees, steep red-rock mountains and sandy washes.Losing the Hammers, one Internet posting read, "would be like baseball losing Wrigley Field or golf losing Augusta."