The Sri Lankan Government and Tamil Tigers kicked off what is expected to be a tense round of peace talks today, with contentious security issues on the agenda for the first time.The run-up to the four days of meetings has been dominated by a dispute over army calls for the rebels to begin disarming in response to Tiger demands the military allow displaced Tamils to return to their homes in High Security Zones in the north. Sri Lankan Prime Minister Ranil Wickremesinghe even issued an appeal on the eve of the talks to not let the dispute derail the peace process he revived when he was elected one year ago. But officials said that under an agenda set after a two-and-a-half-hour meeting between head government negotiator G.L. Peiris and top tiger official Anton Balasingham, humanitarian issues would be discussed first, with security put off until later. ‘‘This session will be more difficult, that can be expected,’’ said Norwegian peace envoy Erik Solheim. ‘‘There is no way in the world anyone can expect a breakthrough at every session,’’ he said.Balasingham has said the resettlement issue had to be dealt with before dealing in depth with so-called core issues. He also warned that the idea of the Tigers giving up their arms was ‘‘non-negotiable.provocative and will not contribute to the creation of a congenial atmosphere for discussions’’.Peiris tried to downplay hopes that the rapid progress would continue at each round of talks. ‘‘We have to recognise the reality that at the end of every session there is not going to be a dramatic breakthrough.’’A truce signed in last February has largely held rebel attacks, with just a handful of deaths last year instead of the usual thousands.