Puppy aggresion

Question
Hello,

We have two american bulldog pups who are 7 months old and from the same litter (boy and girl).  They both are very social with dogs and people but only off the leash.  We have been taking them to a local dog park where they have not exhibited any aggression to other dogs nor to people.  However, when they are on their leashes, and another person or dog whom they don't know approach, they start to act over aggressive - pulling, barking.  They know sit, and will do it when told, but will continue to bark.  Any ideas on how to distract them while on the leash?

Thanks for the help

Answer
You have to take your walks seriously.  You set the pace, choose the direction, etc. They walk along with the leash slack, no sniffing, and no watching things at the side.  When you see something coming that could distract them, start talking to them and be prepared for a leash correction.