In order to achieve that, the Tigers probably want some more military success. There might be a brief period of fighting before any possibility of negotiations resurfaces. Hopefully the fighting, though it may be intense, will be short-lived.
The Tigers are reminding Sri Lanka's new president of their military capability. They're telling the president not to be unrealistic in his dealings with them.
The only thing you can clutch on to is that the situation will get so bad that it will shock the two sides into a new mindset and that will make them more flexible.
There is an argument that both sides are simply going through the motions to convince the international community they have exhausted peaceful options but that both really have decided conflict is inevitable.