WASHINGTON, USA (AFP) — Hollywood legend Clint Eastwood made Mitt Romney's day yesterday, urging Americans to join him in supporting the Republican White House challenger in a TV ad against President Barack Obama.

The gruff-voiced Dirty Harry star said four more years of Obama would mean four more years of policies that have left America "knocked down," with 23 million people unable to find work.

"Our country just couldn't survive that," said Eastwood, 82. "We need someone who can turn it around fast. That man is Mitt Romney. There is not much time left and the future of our country is at stake."

The pro-Republican ad was part of a $12.6 million ad buy from American Crossroads, a so-called super PAC outside group that can accept and spend unlimited contributions, that includes two other spots.

"Bow" pounces on Obama's China policy — "The more Obama borrows from China, the more we'll have to bow to China," a narrator says — while "Survive" targets his alleged lack of support for small business.

The 30-second ads are set to air in seven hotly contested states ahead of the November 6 vote.

Eastwood, whose baseball drama "Trouble with the Curve" is now playing in theaters, rocked the Republican convention in August with an improvised conversation that featured an absent Obama represented by an empty chair.

Earlier in the year, he narrated a patriotic Chrysler car commercial during the Super Bowl — "It's halftime in America (and) the world's gonna hear the roar of our engines" — that pundits read as an implicit plug for Obama.