The UN World Food Program began a major airlift of emergency supplies to earthquake-stricken parts of Pakistan, where survivors remain desperately short of food and shelter.
The United States, meanwhile, shifted military aircraft from neighbouring Afghanistan to the worsening humanitarian crisis.
Japan responded on Tuesday to Pakistan President Pervez Musharraf's appeal for more international aid with a pledge of US$20 million, Chief Cabinet Secretary Hiroyuki Hosoda said.
Hosoda said Japan was ready to provide more help upon request. Defence Agency chief Yoshinori Ono said Tokyo was considering dispatching helicopters for disaster relief.
The Singapore government on Tuesday promised US$200,000 in humanitarian relief for Pakistan.
The UN airlift of supplies began Monday night, and more planes were to arrive Tuesday with medical supplies, generators and high-energy biscuits, the United Nations said.
"It is vital to get to the survivors as soon as possible," WFP chief of operations Jean-Jacques Graisse said in a statement.
Desperate Pakistanis huddled against the cold and some looted food stores Monday because aid still had not reached remote areas of Kashmir, the centre of Saturday's 7.6-magnitude earthquake, which flattened villages, cut off power and water, and killed between 20,000 and 30,000.
Musharraf said his government was doing its best to respond to the crisis. He appealed for international help, particularly for cargo helicopters to reach remote areas cut off by landslides.
"We are doing whatever is humanly possible," Musharraf said. "There should not be any blame game. We are trying to reach all those areas where people need our help."
The International Federation of Red Cross and Red Crescent Societies planned to meet the immediate needs of 120,000 vulnerable people in affected areas, the Australian Red Cross said.
Eight US helicopters-- five Chinook transport choppers and three Black Hawks for heavy lifting-- were diverted from the war in neighbouring Afghanistan. They carried supplies, tarpaulins and equipment, including high-tech cameras for finding buried survivors.
Three US military cargo planes arrived in Islamabad on Monday with blankets, tents, prepared meals, plastic sheeting and water. Four more flights were expected, including one carrying a disaster response team.
US Defence Secretary Donald H. Rumsfeld said Monday he has no concerns that the shift of some supplies to earthquake relief in Pakistan would interfere with military operations in neighbouring Afghanistan.
During a visit to the Pakistani Embassy in Washington, Rumsfeld called the earthquake 'a tragedy of enormous proportions'.
Pakistan also saod it would accept India's offer of aid for victims in the Pakistan-controlled portion of disputed Kashmir.
Pakistani Foreign Minister Khursheed Kasuri said there was no problem accepting aid from India.