Two climbers vying to finish the once-seemingly impossible challenge of scaling a sheer slab of granite in California's Yosemite National Park without climbing aids are closing in on the top of the 3,000-foot (900-meter) peak.

If all goes as planned, 30-year-old Kevin Jorgeson of California and 36-year-old Tommy Caldwell of Colorado, should reach the summit of El Capitan early Wednesday, possibly as early as 1 p.m. said spokeswoman Jess Clayton.

They started Dec. 27 and have been "free-climbing," a technique that shuns climbing aids other than harnesses and ropes to prevent deadly falls.

The world has been watching the pair's grueling half-mile journey up the peak's Dawn Wall route. But Clayton says the men won't give media interviews at the top. They plan to discuss the climb Thursday.

Eric Jorgeson, Kevin Jorgeson's father, told KGO-TV his son has always been a climber and watching him fulfill a long-time dream makes him proud.

"He climbed everything he could think of. It made us nervous early on as parents, but we got used to it," the father said. "It was more other parents saying, 'Hey, your son is at the top of a backstop.'"

The two started climbing El Capitan (there are more than 100 routes to the top) when Kevin Jorgeson turned 15 and it has been a birthday tradition ever since.

Becca Caldwell, who is married to Tommy Caldwell, is also on the ground with their toddler son and has been blogging about her excitement as she prepares to reunite with her husband.