ISLAMABAD (Reuters) – The Asian Development Bank (ADB) is expected to contribute at least $2 billion to help Pakistan recover from its worst ever floods.

The economic costs of the floods are expected to run into the billions of dollars, stepping up pressure on Pakistan`s government just after it had made progress in stabilizing the country through security offensives against Taliban insurgents.

"While the assessment will take several weeks to complete, the damages so far are staggering," said the ADB in a statement on its website.

Aid funding has improved, with nearly half the $459 million needed to fund initial relief efforts secured after days of lobbying donors. But the situation on the ground remained grim.

Only a small minority of the 6 million Pakistanis desperate for food and clean water have received help after floods that have killed up to 1,600 people.

Two million are homeless and disease outbreaks have complicated relief efforts. Flood victims are turning on each other as aid is handed out and anger is rising over the government`s perceived sluggish response to the crisis.

"Over the next two years, ADB`s contribution to the recovery is expected to be at least $2 billion," the Manila-based bank said.

Hundreds of villages are isolated, highways and bridges have been cut in half by floods and hundreds of thousands of cattle -- the livelihoods of many villagers -- have drowned.

Many hospitals and medical camps are overwhelmed and fears are rising for possible epidemics of diseases and viruses such as malaria.