Unfortunately, another wrench was thrown in his plans when Avatar Roku refused to support Sozin's plans. Roku insisted that, as the Avatar, it was his duty not only to remain impartial, but to maintain peace - a responsibility that unequivocally ruled out playing any part in a plot for world domination. Now Sozin was faced with the problem of keeping the Avatar, master of all the elements, from ruining the whole thing. Eliminating Roku seemed impossible; Sozin was certainly a skilled firebender, but Roku was a master firebender, AND a master airbender, waterbender, and earthbender. An outright physical fight was out of the question.
Sozin himself was fond of using violence when eliminating his enemies and obstacles, but royal families were well-versed in the ways of assassination, and some tactics were more subtle than others. Fratricide was one thing, but no one would stand behind a Fire Lord who had the audacity to assassinate the Avatar. People loved the Avatar. Then again, people also loved peace, but they were just going to have to get used to living without that for awhile.
Sozin had done some reading up on exotic Earth Kingdom plants, and was particularly excited to learn about the White Jade bush. Its leaves were highly poisonous, but it also bore a striking resemblance to the White Dragon bush, which was world-reknowned for producing exceptionally delicious tea. Many Earth Kingdom residents had a hard time telling the plants apart (some meeting an untimely fate as a result), and certainly no foreign citizens would be able to tell the difference at a glance.
"Kuzon, take a letter," he ordered, waiving a servant over. "To the attention of Avatar Roku. I have recently received a shipment of imported White Dragon bush leaves from the Earth Kingdom. I am sure you are aware of the reputation preceding this rare plant, and would like to invite you to the Palace of the Fire Lord to enjoy a cup of the most exquisitely delectible tea in the world. I look forward to your company. Sincerely, Fire Lord Sozin." The servant nodded and hurried off to attach the scroll to a messenger hawk. Sozin steepled his fingers and smiled to himself.
"It's tea time."