Sri Lanka has flatly rejected a plan by the United Nations to send a special humanitarian mission to the island's war-torn north.
The UN has called for a series of humanitarian pauses in the fighting to allow the evacuation of up to 50,000 trapped civilians.
The military said an exodus of 103,000 people from the tiny coastal strip had slowed on Thursday, four days after troops blew up an earthen barrier the Liberation Tigers of Tamil Eelam built to stop people from escaping.
UN Secretary-General Ban Ki-moon said he will send a humanitarian team to the area as troops push to end a 25-year war with Tamil Tiger rebels, who want a separatist state.
"So many lives have been sacrificed. There is no time to lose," Mr Ban said on Thursday.
But Human Rights Minister Mahinda Samarasinghe said there is no need for the UN to send people from abroad to visit the area.
He said he agrees in principle that a visit by UN staff based in Sri Lanka can take place, but said intense fighting between troops and the rebels was making it "virtually impossible".
The Sri Lankan government has been blocking most aid agencies from working in the war zone for months, and accuses UN agencies and non-government organisations of supporting the Tamil Tigers.
The army on Thursday said there would be no more breaks in fighting as it closes in on the rebels in the north. Spokesperson Brigadier Shavendra Silva said the only way civilians could leave the area is if the army rescues them, as the rebels would not let any more out.
The rebels, whose fighters wear cyanide capsules to be taken in case of capture, have also ruled out giving up its fight to build a separate state for the Tamil minority. They began fighting in the early 1970s, and has waged a full-blown civil war since 1983.
NZ concern for refugees
New Zealand aid groups Tear Fund and the Red Cross are calling on international agencies to take action to ensure the safety of refugees.
Tear Fund spokesperson Ian McInnes says trapped refugees risk being shot by the Tamil Tigers if they try to flee the war zone.
Mr McInnes says it is important that security groups in Sri Lanka and international agencies seek to protect these civilians and help them to escape from the front-line.
The New Zealand Red Cross says it is particularly concerned about sick, injured and elderly civilians who may not have the strength to trek to safety.
Earlier this week, the International Committee of the Red Cross said fighting had killed several hundred people. A land and sea battle on Wednesday blocked the evacuation of wounded by sea and the delivery of aid supplies by a ship, it said.