Surface-to-air missiles could be deployed at six sites across London during the Olympics, the Ministry of Defence said today.
The Lexington Building in Tower Hamlets and the Fred Wigg Tower in Waltham Forest, both in east London, have been identified as potential sites.
Blackheath Common and Oxleas Wood, both in south east London, plus William Girling Reservoir in the Lea Valley Reservoir Chain in Enfield and Barn Hill at Netherhouse Farm in Epping Forest are other possible sites.
These are all potential locations for ground-based air defence systems, should the Government decide to deploy them during the Games.
No final decision has been made about this potential deployment but it does form part of Olympic Guardian, a major exercise in which security preparations are being tested this week.
Both military and civilian personnel are working on the exercise, which takes place on land, sea and in the air in London and Weymouth.
A wide range of actions and capabilities will be tested over nine days.
Defence Secretary Philip Hammond said: "Support for the Olympic Games will be an important task for defence in 2012 and this exercise is about pushing our people and our systems to the limit to ensure that we are ready for the challenge.
"The majority of this exercise will be played out in full view of the public and I hope that it will have a secondary effect of reassuring the British people that everything possible is being done to ensure this will be a safe and secure Olympic and Paralympic Games."
On whose decision it would be to deploy the missiles, standing joint commander General Sir Nick Parker said it would be taken "at the very highest political level".
Talks have taken place with housing associations, and leaflets will be sent out to keep the public informed.