Winger Mathew Leckie scores with a smart run and finish to extinguish Denmark's FIFA World Cup hopes, setting stage for a clash with Argentina in the knockout round.

Australia have now won back-to-back World Cup games for the first time.
Australia have now won back-to-back World Cup games for the first time. (Reuters)

Australia coach Graham Arnold has hailed the Socceroos' "remarkable" achievement after they reached the last 16 of the World Cup for only the second time with a 1-0 win over Denmark.

Winger Mathew Leckie scored the winner on the hour with a smart run and finish to extinguish Denmark's Qatar hopes at the group stage on Wednesday.

Australia, who made the knockout rounds in 2006 when they had Harry Kewell, Tim Cahill and Mark Viduka in their ranks, have now won back-to-back World Cup games for the first time.

The current Australia team do not have the stars of yesteryear, but they make up for it with spirit and hard work and showed flashes of quality in a strangely subdued encounter.

"I am just so proud of the players' work ethic, their commitment, their fight," said Arnold, who was assistant to Guus Hiddink during Australia's run to the last 16 in Germany in 2006.

"We had some moments there (against Denmark), but defensively we were outstanding tonight."

The 59-year-old, whose side was thumped 4-1 by France at the start of the tournament, added, "I truly believe that the Socceroos are the team that unite the nation."

"Maybe we are talking about a new 'golden generation' now," he added, nodding to the stars of 16 years ago.

Australia is set to clash with Argentina in the round of 16 after the Albicelestes beat Poland 2-0.

Emotionally overcome

European Championship semi-finalists Denmark, who had to win to stand any chance of going through, were on top in the early stages.

Mathias Jensen, Brentford's midfielder, had one of his team’s best game chances in the 10th minute, but Australia goalkeeper Matthew Ryan came up with a point-blank save.

Socceroos captain Ryan was in the thick of it again soon afterwards, frantically hacking the ball away with his feet after an incisive run down the left by Joakim Maehle.

Australia were just about on top when a sterile first half meandered to a goalless conclusion.

Leckie found himself one-on-one with an exposed Maehle on the left and turned him inside out before pinging the ball into the bottom corner past goalkeeper Kasper Schmeichel. Cue pandemonium from the Australian bench.

The 31-year-old Leckie said he was so emotionally overcome that he did not know how to celebrate.

"I didn't really know what to do so I just pounded my chest," he said, as Australia's substitutes poured off the bench to congratulate him.

"It just shows what a team we are, everyone is here for each other."

Denmark's disappointment

Denmark are 10th in the FIFA rankings and, following their run to the last four at the Euros last year, had been touted by some as dark horses in Qatar.

Coach Kasper Hjulmand was at a loss to explain how his team had exited the tournament with just a solitary point.

They barely put up a fight as their World Cup hopes slipped away.

"It really irritates and frustrates me, and I am really sad," he said.

Hjulmand added, "There is no doubt that we did not reach our level ... it is my responsibility. There was too much emotion and too little quality."

"All my waking hours I tried to prepare as best I could," he said. "There was a lack of enthusiasm and coherence ... where did that come from?"

Source: TRTWorld and agencies