Hopes for a lasting peace in the war between the Tamil Tigers and the Sinhalese majority government are dimming as the opposition withdrew its support of the government’s effort to rejuvenate peace talks. The Tigers are warning that war could resume, roadblocks have returned to Colombo after a series of killings, and Norwegian mediators, who were instrumental in securing a truce two years ago, have warned that without help from the opposition, the gains toward peace could be lost.