The United Nations Secretary General Ban Ki-moon has arrived Pakistan Sunday morning to express solidarity with 20 million flood-affected people experiencing the worst ever floods in the country's history.

"I am here for second time in Pakistan to show my sympathy and to urge world community to help Pakistan," Ban told reporters soon after coming out of the Pakistan Air Force (PAF) plane on Sunday morning at Chaklala Air Force Base near the capital city Islamabad.

Earlier reports said that the UN Secretary General would arrive in Islamabad on Saturday. No explanations have been given to his delayed arrival. It could be due to weather reasons as it was raining heavily in Islamabad on Saturday.

The UN Secretary General reportedly arrived in Islamabad Sunday morning from Dubai. Shortly after his arrival, he held a meeting with the Pakistani prime minister Gilani. During his brief stay in Pakistan, the UN Secretary General will also call on the Pakistani president Asif Ali Zardari, take an aerial view of the flood- affected areas in southern Punjab province and may give a press conference upon his departure.

During the meeting with the Pakistani prime minister Gilani, the UN chief said that UN is trying to fully mobilize all possible resources to help Pakistan.

"My visit will send a message of gravity of situation in Pakistan," said the UN Secretary General, adding that he came here to personally express solidarity with Pakistan.

Earlier upon his arrival in Islamabad, the UN Secretary General told the local media that he would report to the General Assembly on Thursday about his visit to mobilize all necessary assistance to Pakistan.

Gilani briefed the UN Secretary General about the damage that the flooding has done to his country. He said all political forces in the country are united to help the flood-affected people at this time.

He thanked the UN Secretary General about the immediate aid provided by UN to Pakistan. He said that the challenges facing the government are to stop epidemic and rehabilitation of the affected people.

The UN Secretary General's visit came days after UN launched an appeal for 460 million U.S. dollars to help Pakistan tackle the needs of flood-affected families.

Elisabeth Byrs of the Office for the Coordination of Humanitarian Affairs (OCHA) said that so far 20 percent of the requested amount has been received.

The funds requested under the emergency response plan launched in New York on Wednesday covers immediate priorities such as food, clean drinking water, tents and other shelter and non-food items as well as medical supplies for those affected by the flooding, which began late last month in the wake of heavy monsoon rains.

OCHA says that the floods have destroyed homes, farmland and major infrastructure in large parts of the country, most notably the northwest province of Khyber Pakhtunkhwa.

UNHCR's Representative in Pakistan Mengesha Kebede said the crisis facing the country is enormous and warned that it will not be over when the flood waters recede.

"We believe that many more communities and refugee camps will literally surface, homes destroyed or very seriously damaged, with hunger and illness exposing in particular women and children to grave situations," said Mengesha.

World Health Organization says one of the major concerns for it is the rising number of people seeking care for waterborne diseases. Several deaths related to waterborne diseases have been reported in the country.

Since the end-July, Pakistan has been hit by heavy monsoon rains and serious floods. To date, the floods have killed 1,384 people, injured 1,630 others and damaged over 700,000 homes across the country, according to the figures revealed by the Pakistani prime minister in his Saturday televised national address. The prime minister said that the natural calamity has affected approximately 20 million people in his country.