Chris.
I'm sorry but you may have to ditch unless you get a really good tail wind or drop your speed.
The range of the A340-600 is maxed out at 7900nm, of course you need to fly 8400nm and that's if you flew directly between the two airports without following airways etc...... I'm not saying it can't be done, it depends on your passenger/cargo load etc, but if you are fully loaded then you may want to say a prayer or two!!!!
This said, so long as you watch your consumption and measure your speed to match it, I think you might make it but you will need to be very alert and have an alternate picked out for a refuel stop about 1000nm short of your planned route. (It will really depend on the winds and weather)
Good luck.