(Reuters) - Striker Romelu Lukaku is set to return but concern over captain Vincent Kompany is still clouding Belgium's build-up to their World Cup last-16 meeting with the United States in Salvador on Tuesday.

Kompany skipped training again on Sunday as he battled with a groin problem, having now not worked out with the rest of the squad since before Belgium's last game against South Korea which he sat out.

Coach Marc Wilmots suggested Lukaku would be restored to the starting line-up for the match at the Fonte Nova arena after also missing the 1-0 win which ensured Belgium a 100 percent record in the first round.

This is despite the poor form in Brazil and the petulance shown by Lukaku when he was taken off against Russia in Rio de Janeiro last Sunday.

The striker jerked his arm away as Wilmots reached over to grab it and shake his hand after taking Lukaku off for a second successive match.

But it seemed to have been forgotten at a news conference at Mogi das Cruzes on Sunday.

"I still count on him," Wilmots said.

"The ankle injury he suffered against Tunisia (in Belgium's last warm-up international before the World Cup) slowed him down. That you can clearly see here. Previously, he had good momentum but now we need to give a boost to his mental confidence.

"Vincent is following a special program," Wilmots added of his captain's condition.

"I hope he'll be able to train tomorrow. He is on track and feels better. He's been working in the swimming pool and done two sessions daily outside as well."