Kiwi drivers Brendon Hartley and Earl Bamber have all but wrapped up the World Endurance Championship title after notching a fourth successive win.

Hartley, Bamber and German Timo Bernhard powered their Porsche hybrid vehicle to victory at the United States leg of the series at the Circuit of the Americas in Texas to open up a commanding lead.

The trio have racked up wins at Le Mans, Nurburgring and Mexico to open a cavernous advantage back to their nearest rivals from Toyota.

It would take a catastrophe in the final legs in Japan, China and Bahrain to prevent victory.