Australia slid to a 1-0 deficit in their Davis Cup tie with Belgium when Lleyton Hewitt lost his opening singles rubber to Kristof Vliegen in a four-hour marathon.

The Belgian, ranked 23 places below Hewitt at No.41, upset the Australian 4-6 6-4 3-6 6-3 6-4 in the World Group first-round on clay at Liege's Country Hall.

Hewitt broke Vliegen's first service game for a 2-0 lead, but the Belgian broke back immediately and then held serve to draw level at 2-2.

In a dogged fifth game lasting 15 minutes, Hewitt finally prevailed before making the crucial break in the sixth.

A double fault from Hewitt took the scores to deuce in the ninth game before he sent a backhand long and gave Vliegen the break.

Hewitt broke back again, however, to claim the gruelling first set in an hour and six minutes.

Vliegen mixed up his shots superbly - he wasn't afraid to come into the net, or force his opponent to do the same - and was rewarded with a vital break in the ninth game of the second set.

Hewitt saved two set points to take the 10th game to deuce but Vliegen took the advantage and won the set when Hewitt sent a forehand wide.

It looked like the turning point might have come when a fired-up Hewitt broke Vliegen in the sixth game of the third set and then held serve to love in the seventh.

But the Belgian refused to go quietly and saved a break point.

When Hewitt double faulted to go 0-30 down in the ninth game, the Australian hit back with an ace.

Hewitt then had to save a break point before claiming the set for a 2-1 advantage when Vliegen hit a backhand return into the net.

Vliegen raced to a 4-0 lead in the fourth set while Hewitt struggled with his serve.

The Belgian levelled at two sets all by claiming the ninth game to love with a forehand winner that sailed deep into Hewitt's back court.

Hewitt looked spent in the decider and was broken straight away as his serve continued to struggle.

He fought back hard but was unable to convert a break point in the eighth game.

Serving for the match, Vliegen had to save three break points before sealing victory with an ace after four hours, 19 minutes.

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