UN chief Antonio Guterres will visit Pakistan next week in "solidarity" with victims of relentless monsoon rains that have flooded a third of the country and killed more than 1,100 people, his spokesman said Tuesday.

"With the tragic situation facing millions of men, women and children impacted by historic floods in Pakistan, the Secretary-General will travel to the country next week for a solidarity visit," Stephane Dujarric told a news briefing.

Guterres plans to arrive in the capital Islamabad on September 9, before travelling to "the areas most impacted by this unprecedented climate catastrophe," Dujarric said.

There he will meet displaced families and humanitarian agencies working on the ground.

As the United Nations appealed for $160 million in aid to help Pakistanis most impacted by the disaster, Guterres warned that the international community needs to do more to combat global warming and its impacts.

"It is outrageous that climate action is being put on the back burner as global emissions of greenhouse gases are still rising, putting all of us -- everywhere -- in growing danger," he said.

The rains that began in June have unleashed Pakistan's worst flooding in more than a decade, washing away swathes of vital crops and damaging or destroying more than a million homes.

Authorities and charities are struggling to accelerate aid delivery to more than 33 million people, a challenging task in areas cut off because many roads and bridges have been critically damaged.