NBA superstar Luka Doncic and Slovenia need just more one win to be guaranteed a medal in their Olympic basketball debut.

Doncic had 20 points, 11 assists and eight rebounds as Slovenia beat Germany 94-70 on Tuesday in the opening game of the men's quarter-finals.

Zoran Dragic got Slovenia off to a fast start by making his first six shots and finished 11 for 13 en route to his 27 points.

The Slovenians will face either unbeaten France or Italy on Thursday in the semi-finals.

They are 17-0 in competition with Doncic, now looking to add Olympic gold to the European championship they won in 2017.

"It's unbelievable; a country of two million being top four in the world," Doncic said.

"It's something unbelievable; we already achieved a lot just going to the Olympics, it's our first time here.

"I wish, I wish (we can get two more wins), but it's going to be really tough, but we're going to be ready and we've got nothing to lose."

Slovenia won their group by outlasting world champion Spain 95-87 on Sunday to earn one of the top seeds, avoiding having to play the US, France or Australia until the semis.

Australia play Argentina in their quarter-final later on Tuesday and, if successful, will face the United States, who rallied from 10 points down in the second quarter to beat Spain 95-81.

Doncic was the leading scorer in the tournament with 28.3 points per game through the group stage.

For the second straight game, he finished just shy of the first triple-double in the Olympics since LeBron James for the US in 2012.

Maodo Lo scored 11 points as Germany wrapped up its first Olympic appearance since 2008, when it was led by Dirk Nowitzki, Doncic's teammate during his rookie NBA season in Dallas.