Fighting in Sri Lanka's war showed no signs of abating on Thursday despite strong words from Barack Obama and the UN.Security Council, with both sides refusing to budge in the waning days of a 25-year conflict. The Security Council and Obama on Wednesday urged the Liberation Tigers of Tamil Eelam (LTTE) to surrender and free tens of thousands of civilians they are holding, and the military to stop shelling people and refrain from using heavy weapons. The International Committee of the Red Cross (ICRC) said fighting on Thursday had blocked it for a third day from offloading a cargo of relief supplies and ferrying out sick and wounded people. “The situation is becoming desperate with the fighting continuing intensely and uninterrupted,” ICRC spokeswoman Sarasi Wijeratne said in Colombo. A Red Cross worker was killed in fighting on Wednesday, the third this year. Late on Wednesday, US President Obama at the White House warned the “humanitarian crisis could turn into a catastrophe,” as fighting intensified and Asia's longest modern war headed to its final act. Reports that hundreds were killed in attacks on a makeshift clinic in the 2.5 square km of remaining LTTE territory, for which both sides blamed the other, prompted the Security Council to make its first formal statement this year. Sri Lanka again ruled out any further truce and insisted troops were only using small arms, while applauding the calls for the LTTE to surrender. “We will cease operations simultaneously when the LTTE lays down arms and surrenders...,” Mahinda Samarasinghe, disaster management and human rights minister, said.