Belgium have sought to project an image of calm after losing their opening game at the European Championship but must be worried about yet another early tournament elimination as they prepare to face Romania in Cologne on Saturday.

A surprise defeat to Slovakia has Belgium on the back foot in Group E and they now face a buoyant Romania, who stunned Ukraine 3-0 on Monday.

"I can't tell the team much about what needed to be better," said coach Domenico Tedesco after their loss, where missed opportunities came back to haunt the much-fancied Belgians.

Jan Vertonghen said Belgium certainly have the players to get a result.

"I would be worried if we didn't have the quality, so I'm confident we will score on Saturday," added the veteran defender in the build-up to the game.

Despite that confidence, Belgium will be fretting over the potential for another early exit after crashing out at the first hurdle at the World Cup in Qatar less than two years ago.

Given the array of quality at their disposal, and after going through the qualifiers unbeaten, Belgium would be expected to advance but top scorer Romelu Lukaku needs to find his range while captain Kevin De Bruyne must increase the tempo in the midfield if they are to dominate Romania.

Victory over Ukraine was only the second time that Romania had won a match at a European Championship and came 24 years after their first -- a 3-2 win over England at Euro 2000.

Captain and Man of the Match Nicolae Stanciu set them on their way to a memorable triumph over Ukraine in their opener on Monday with a cracking long-range strike and he will have added motivation to try to repeat that against Belgium.

Stanciu was the most expensive transfer in Belgian club football when he moved to Anderlecht in 2016 but was later dubbed a 10 million euros ($10.73 million) flop and sold after 18 months.

Romania, who have other potential match winners such as Denis Dragus and Valentin Mihaila, went through the qualifying campaign unbeaten and finished top of their group ahead of Switzerland and have lost only once in their past 16 games.

"This is the generation of the soul - this team has put the biggest effort into everything,” Romania coach Edward Iordanescu said after they beat Ukraine.

He will surely be even more gushing if Belgium are added to their list of conquests.