GELSENKIRCHEN, June 12 - Czech striker Jan Koller was carried off against the United States on Monday with a thigh injury that could rule him out of the rest of the World Cup.

Koller, who had put the Czechs ahead with an early goal, looked in considerable pain as he was carried from the pitch just before halftime with an ice pack strapped to the back of his leg.

Koller had suffered a lengthy lay-off with a serious knee injury before the tournament.

His injury is bad news for the Czechs, whose strike force has already been depleted by Milan Baros's struggle to shake off a foot injury.

As the Czech Republic's top all-time goalscorer, Koller is a key part of a team aiming to build on a superb showing at Euro 2004 where they reached the semi-finals.

Italy and Ghana are the other teams in Group E.