The Chelsea loanee withdrew from international duty this week due to an ankle injury, and will be monitored ahead of the Premier League champions' visit on Saturday
Lukaku missed the recent international break with Belgium after taking a knock to his ankle in training and aggravating the injury against QPR before the break.
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"We're hopeful Lukaku will be fit. He's had a pain in his ankle for a few weeks. He felt it again when he came off the bench against QPR and didn't feel it was right to go," Clarke told the club's official website.
"He went across and got it assessed by the Belgium doctor and got sent back.
"It's not a big problem but it's one we're mindful we don't want to become a big problem. We're monitoring it."
West Brom are also close to welcoming back Jerome Thomas from injury after a minor operation that has disrupted his season so far.
Clarke revealed: "Jerome trained last week and is on the way back."