Two men have slowly been making their way up 900m of granite as they climb the Dawn Wall of El Capitan, a rock formation in California's Yosemite National Park.

Tommy Caldwell and Kevin Jorgeson are set to become the first people to free-climb the rock face using only ropes to catch them if they fall.

They are very close to completing this nerve-wracking climb and should reach the top on Wednesday.

Alistair Leithead reports.