WASHINGTON (AFP) - The United States on Wednesday denounced the international response to Pakistans humanitarian crisis as inadequate, with a senator saying that Gulf Arab states should contribute more. The United Nations in May appealed for $543 million to help the nearly two million people displaced by fighting in northwestern Pakistan. UN figures show that less than 38 per cent of the appeal has been met. The top US diplomat on refugee issues said that the United States had more than met its responsibilities with more than $320m for Pakistan - much of it not channelled through the UN appeal. The humanitarian response has been inadequate, Assistant Secretary of State Eric Schwartz told a congressional hearing. Other countries must come forward to help. This was one of the largest rapid displacements of people in recent memory, he said. Pakistani authorities have responded effectively and returns have begun, but there are still 1.5 million people who have not returned. The massive displacement came after Pakistan, under US pressure, launched a major offensive against Taliban fighters who had advanced perilously close to Islamabad, capital of the Islamic worlds only declared nuclear power. Senator Bob Casey, who led the hearing, said that Gulf Arab states, most of which have large South Asian work forces, should give more money to relief efforts. Ive been disappointed, to say the least, by the lacklustre response by the international community to date, especially that of the Gulf states, said Casey, a member of President Barack Obamas Democratic Party. Were not talking about military forces here - just financial assistance. Its time our allies and friends step up to the plate, he said. Richard Holbrooke, the US special envoy for the region, highlighted funding concerns on a visit this week to Brussels to meet with European Union and Nato officials. The European Union has contributed more than $212m. EU foreign policy chief Javier Solana said on a visit to a displacement camp last week that the bloc would continue to support Pakistan.