Justin Leonard and Hunter Mahan drew first blood for the United States with a 3&2 victory over Britain's Paul Casey and Swede Henrik Stenson in the opening foursomes matches at the Ryder Cup on Friday.

Leonard and rookie Mahan shrugged off a bogey-bogey start at a sun-drenched Valhalla Golf Club to seal the win with a regulation par on the 16th green.

"It feels great," Leonard said in a greenside interview. "I told Hunter I lost the first two holes for us on purpose to take the pressure off. We had a lot of fun out there."

The Americans, who had trailed holders Europe early on in three of the four alternate shot encounters, were up in two and level in one in the remaining matches.

Kenny Perry and Jim Furyk led Spaniard Sergio Garcia and Britain's Lee Westwood by one after 13 holes while Stewart Cink and Chad Campbell were one up on British duo Ian Poulter and rookie Justin Rose after 14.

In the top contest, Irishman Padraig Harrington and Swede Robert Karlsson were all square with Phil Mickelson and rookie Anthony Kim with two holes to play.

The European combination had forged three up after 12 holes before Mickelson and Kim fought back, winning the 13 and 14 with pars.

Mickelson then rolled in a 20-footer to birdie the 15th and pumped his left fist in celebration.

Europe are bidding for an unprecedented fourth consecutive Ryder Cup victory while the United States are seeking their first triumph since their come-from-behind success at Brookline in 1999.

The Americans have not won an opening session in the biennial competition since the 1991 matches at Kiawah Island.

However, U.S. captain Paul Azinger believes his team have everything to gain as underdogs against Europe while missing Tiger Woods for the first time since he made his Cup debut in 1997.

"The Europeans have brought an incredible team over here and we have a great opportunity to change it," he said.

"We have everything to gain in this situation. Not a lot of people expect us to pull this off, minus Tiger Woods. Everybody feels pressure but hopefully they (my players) will be free-wheeling out there. That's my hope."