MELBOURNE, AUSTRALIA - MARCH 06: John Isner of the USA hits a forehand volley in his match against Bernard Tomic of Australia during the Davis Cup tie between Australia and the United States at Kooyong on March 6, 2016 in Melbourne, Australia. (Photo by Michael Dodge/Getty Images)

John Isner has sealed a first round win for the USA over Australia with a four-set win over Bernard Tomic, sending Australia packing from the Davis Cup.

Isner claimed the first two sets over an out of sorts and lethargic Tomic, before the young Aussie fought back to claim the third set and give the home side a sniff of taking it to a deciding fifth rubber.

However, it was too little too late, as Isner rallied to claim the fourth set in a tiebreak and record a 6-4, 6-4, 5-7, 7-6 win to give the United State an unassailable 3-1 lead in the tie.

But the major talking point from the match will unforgettably be Tomic's mid match dig at Davis Cup teammate Nick Kyrgios.

Tomic was heard by courtside microphones voicing his annoyance at the absence of Kygrios from the team to Australian captain Lleyton Hewitt.

"Nick's sitting down in Canberra. Bulls*** he's sick," Tomic said.

"Two times Nick's done it."

The US face either Croatia or Belgium in the quarter-finals.

Full results:

Day one

John Isner (USA) def Sam Groth (AUS) 7-6, 6-2, 6-2

Bernard Tomic (AUS) def Jack Sock (USA) 7-6, 6-3, 3-6, 6-4

Day two

Bob Bryan/Mike Bryan (USA) def Lleyton Hewitt/John Peers (AUS) 6-3, 6-3, 4-6, 4-6, 6-3

Day three

John Isner (USA) def Bernard Tomic (AUS) 6-4, 6-4, 5-7, 7-6