POREC -- Croatia, the 2005 champions, opened up a 2-0 lead over the United States in their Davis Cup World Group quarterfinal here early on Saturday.

Ivo Karlovic came from two-sets down to defeat James Blake and give Croatia a 1-0 lead.

Karlovic won 6-7 (5/7), 4-6, 6-3, 7-6 (7/3), 7-5 in a match that lasted three hours and 37 minutes.

"It was a very long match and it was not easy for me. I was very nervous at the start since I was playing in front of the local crowd," said Karlovic, the world number 27.

"I needed some time to relax and then I achieved one of the most important victories in my career."

In Friday's second rubber, Marin Cilic beat Mardy Fish 4-6, 6-3, 6-7 (2/7), 6-1, 8-6 in a match which lasted four hours and 24 minutes and ended early on Saturday.

In the decisive fifth set, Cilic broke to lead 5-3. Fish replied, took Cilic's serve and held for 5-5.

But the crucial second point in the tie for Croatia was won by Cilic with his more aggressive game paying dividends on Fish's serve for 8-6.

"At the beginning I had a lot of problems with mobility," Cilic said. "It was in the fourth set that I started to play as I wanted to."

US captain Patrick McEnroe told Croatian television he was unhappy with the results.

"Hopefully tomorrow we can win one rubber and make it 2-1," McEnroe said.

On Saturday, Karlovic and Lovro Zovko face Wimbledon runners-up Bob and Mike Bryan in the doubles.

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.