FOXBOROUGH, Massachusetts (Reuters) - Two goals by Santi Cazorla and one apiece from Alvaro Negredo and Fernando Torres led world champions Spain to a 4-0 rout of United States in a friendly on Saturday.

Spain were 3-0 up at halftime in front of a 64,121 crowd and it could have been even more after David Villa had a goal harshly disallowed for offside and Negredo clipped the crossbar.

U.S. coach Bob Bradley opted to leave a number of regular starters on the bench and was perhaps regretting that decision when Negredo was allowed to run unchallenged through the middle and finished coolly to make it 2-0 in the 32nd minute.

Cazorla added a third goal after more good work from Negredo and Silva.

Bradley brought on Clint Dempsey, the coach's son Michael and experienced defender Steve Cherundolo at the break and that helped tighten things up.

But Spain continued to play with their characteristic precision passing and added a fourth goal in the 73rd minute through Torres, who latched on to a defense-splitting pass from Borja Valero to beat keeper Tim Howard.

The defeat was a blow to the U.S. who start their CONCACAF Gold Cup campaign against Canada on Tuesday, the same day as Spain play another friendly in Venezuela.

(Editing by Tony Jimenez)