California's high-speed rail project reaches a milestone with officials breaking ground on the nation's first bullet train.

The ceremony in Fresno on Tuesday comes amid challenges from Central Valley farmers and communities in the train's path who have sued to block the project; Republican members of Congress vow to cut funding.

State officials say once it's built, the $68 billion train system will whisk travelers at 200 mph between Los Angeles and San Francisco in less than three hours.

Dan Richard of the California High-Speed Rail Authority says it will be a model for the nation.

Jeff Denham, a Central Valley Republican in Congress, says the train won't be fast enough or carry enough riders.

Gov. Jerry Brown, a staunch advocate of the train, is expected to attend the groundbreaking.