ISLAMABAD (AP) — Pakistani Prime Minister Shahbaz Sharif told an American diplomat Thursday that the world must step up its fight against climate change to avoid more deadly flooding in the impoverished Islamic nation, the government said.

Sharif made the comment in a meeting with Derek Chollet, a senior State Department official visiting Islamabad to assess damages and arrange for aid in the wake of floods that have killed 1,355 people, affected 3.3 million people and made more than half a million homeless.

According to the statement, Chollet “affirmed that the U.S. would stand by Pakistan in the wake of this immense challenge, extend vital support, and help affected people rebuild their lives and communities.”

The meeting came a day ahead of the first American planeload expected to arrive in Pakistan with supplies. U.N. Secretary-General Antonio Guterres also was to arrive in Pakistan Friday to travel to flood-hit areas.

Guterres is arriving in Pakistan less than two weeks after he issued an appeal for $160 million in emergency funding to help millions affected by record-breaking floods that have caused at least $10 billion in damages.

Last week, Guterres warned about the effects of climate change in the future.

“Let’s stop sleepwalking toward the destruction of our planet by climate change,” he said on August 31 in a video message to a ceremony in Islamabad. “Today, it’s Pakistan. Tomorrow, it could be your country,” he said at the time.

So far, U.N. agencies and several countries have sent dozens of planeloads of aid to Pakistani flood victims. Washington has announced the U.S. will provide $30 million in assistance to help victims of the flood.

The catastrophe has added new burdens to the cash-strapped Pakistan and highlighted the disproportionate effect of climate change on improverished populations. Experts say Pakistan is responsible for only 0.4% of the world’s historic emissions blamed for climate change. The U.S. is responsible for 21.5%, China for 16.5% and the EU 15%.