Britain says it is ready to provide extra military personnel to help secure the upcoming Olympic games, after a private contractor reported problems with fielding a large enough force.

The government said an extra 3,500 troops will be available for the event, which begins July 27.

Security company G4S says it is continuing to work on resolving manpower and scheduling issues that arose in the past few weeks. It called recruitment for the security effort “unprecedented and very complex.”

Britain had already pledged 13,500 troops and $857 million for venue security.