The world's top-ranked doubles team of Bob and Mike Bryan kept the USA alive in their Davis Cup quarter-final against Croatia with a 6-3 6-1 6-3 win over Roko Karanusic and Lovro Zovko.
Croatia still lead the tie 2-1 ahead of the reverse singles.
Unlike Friday's marathon singles rubbers, Saturday's doubles lasted just 68 minutes with last weekend's Wimbledon runners-up in total control.
In the reverse singles Marin Cilic opens against James Blake with Ivo Karlovic facing Mardy Fish.
The Americans, who are missing injured Wimbledon finalist Andy Roddick, are bidding to defeat Croatia for the first time, having lost to them in the first round in 2003 and 2005.