Britain has again upgraded its security plan to protect athletes and visitors at this summer's 2012 Olympics in London.

Defense Secretary Philip Hammond told lawmakers Thursday that Britain now plans to deploy 13,500 troops for the Games. The military mix will include ground troops, Typhoon fighter jets, helicopters, two warships and bomb disposal experts.

Earlier this month, Olympic officials more than doubled the amount of police and private security personnel from 10,000 to over 22,000. The military contingent will be in addition to the police and private security presence.

Hammond's announcement follows concerns that the earlier plan would still not be sufficient to guard against possible security threats. About 7,500 troops will work directly on guarding more than 100 venues to protect them against car bombs or other attempted terrorist attacks.

Olympic officials had already budgeted $1.6 billion for security.

HMS Ocean, the largest ship in the Royal Navy's fleet, will be berthed in Greenwich, in east London. It will act as a helicopter landing site and a logistics center, while the HMS Bulwark warship will act as a maritime command post in Weymouth. Typhoon fighter jets will be moved to the Royal Air Force's Northolt base in north London.