The United Nations has launched an appeal for more than 450 million dollars to help those affected by floods in Pakistan. The money is for immediate relief in the next three months. The UN relief coordinator, John Holmes described the floods in Pakistan as one of the most challenging that any country has faced in recent years adding that the need for aid is critical. He said, unless aid activity is continued to be rapidly scaled up to reach those who remained displaced, additional loss of human lives and further suffering will occur.The UK responded to the UN appeal by announcing it would supply aid to some 1.5 million people in Pakistan.Four more plane loads of relief supplies will be sent, said the Secretary of State for International Development, Andrew Mitchell. The US has deployed a carrier to Pakistan that will triple the number of American helicopters available for use in the flood relief effort, Defence Secretary Robert Gates was quoted as saying in Florida by AFP news agency.US helicopters have already been helping in northern parts of Khyber Pakhtunkhwa province. So far, about 1,600 people have been killed by the monsoon floods. Weather officials say the monsoon system over the Arabian Sea is weakening and there should be a break in the torrential rains for at least the next three days, though scattered rains are forecast.