Jordan Thompson and Nick Kyrgios gave Australia a 2-0 lead over the United States in their Davis Cup tennis quarterfinal tie with hard-fought singles victories here on Friday.

The 79th-ranked Thompson squared off against American No.1 Jack Sock in the first match, played on an outdoor hard court at Pat Rafter Arena in this eastern city, and pulled off a key upset 6-3, 3-6, 7-6 (7-4), 6-4, reports Efe.

The 15th-ranked Sock, who possesses one of tennis' biggest forehands, hit twice as many winners as Thompson off that wing (24 to 12) and controlled his service games for the most part, winning more than 70 percent of both his first-serve and second-serve points.

But Thompson was more opportunistic when he was able to go deep in Sock's service games, converting four of his six break-point chances.

Though slighter of build than his opponent, the Australian also showed surprising power on the serve, throwing down 14 aces to the American's seven.

Friday's second singles match pitted two of tennis' most dominant servers, the 16th-ranked Kyrgios and 23rd-ranked American John Isner.

The Australian had the key edge, however, in the athleticism department and used his all-around game to edge his rival 7-5, 7-6 (7-5), 7-6 (7-5).

Kyrgios had numerous chances to break Isner's serve throughout the match, although both of his service breaks came in the first set. Isner also got his lone service break that set but then did not have a single break-point opportunity over the final two sets.

The Australian went down a mini-break with Isner serving at 5-4 in the final tiebreaker, but he connected on two clutch return of serves to give himself a match point and then clinched the victory with his 20th ace.

"I feel I played well enough to beat a lot of players out there today," Isner was quoted as saying on the Davis Cup's official Web site. "Those two returns at 5-4 and 5-all were pretty high quality and he did it."

The host nation, which has won tennis' premier international team event 28 times, now needs just one more win for a berth in the Davis Cup semifinals.

This quarter-final tie is a battle between the two most successful countries in Davis Cup history, with the Americans having won a record 32 titles, the most recent coming in 2007.

Australia last won the Davis Cup in 2003.