USA boss Juergen Klinsmann is taking a cautious approach with Jozy Altidore.
The Sunderland striker was cleared of serious hamstring damage earlier this week but remains under a fitness cloud for Friday's World Cup qualifier with Costa Rica in San Jose.
"We take it day by day. Today will be another big step," Klinsmann said ahead of a training session on Thursday.
"Everything is healed with the hamstring issue. We did an MRI. We did tests. Nothing can happen, but he hasn't trained in a full rhythm for seven, eight days."
Altidore has been stellar form for the US recently, scoring seven goals in his past five matches, including a hat-trick in a 4-3 friendly win over Bosnia last month.
