A senior United Nations official has criticised the "quite extraordinary" lack of international support for Pakistan in its struggle to deal with devastating floods. Louis-George Arsenault, the director of emergency services for Unicef, said the flooding was the biggest humanitarian crisis in decades. "One of the major challenges that we have, which is quite extraordinary, is the lack of level of support from the international community," he was quoted as saying by the Guardian. "Right now, our level of needs in terms of funding is huge compared to what we've been receiving - even though this is the largest, by far, humanitarian crisis we've seen in decades." His comments came as the International Monetary Fund prepared to meet Pakistani officials in Washington to hold talks about measures to stave off an economic crisis in the aftermath of the devastation. The UK Disasters Emergency Committee (DEC), the umbrella organisation for aid agencies, will also renew its appeal for help, which has already prompted 24m in donations. Tens of thousands of people are trying to flee the latest flood surge in southern Pakistan, three weeks after huge monsoon rainfall hit the country. About 1,600 people are thought to have died and an estimated 20 million have been affected by the disaster. The World Health Organisation has warned that diseases are spreading, with hundreds of hospitals and clinics damaged or destroyed. The UN says it has so far raised about 70% of the $460m (295m) it had set as an aid target. Britain has earmarked up to 64.3m, with 16.8m already committed to providing tents, blankets, food supplements for babies and other relief. A separate 10m bridge-building project has also been brought forward. The DEC money is not included in this sum.