The United States has announced more than $US1 billion ($A1.4 billion) in humanitarian and disaster response assistance for UNICEF and the World Food Program.

The funding is intended to support life-saving assistance in more than 40 countries, the US State Department said on Tuesday.

More than $US800 million ($A1.1 billion) will go to the WFP, while the UN children's agency UNICEF will receive more than $US218 million ($A308 million), according to the statement.

The announcement comes one month after the US said it would provide $US1.8 billion ($A2.5 billion) to the United Nations.

In December, the Trump administration announced $US2 billion ($A2.8 billion) in funding.

Before Donald Trump took office, US financial contributions to the UN had at times been significantly higher.

The US also still owes billions of dollars in membership contributions to the UN, which is under severe financial pressure and has repeatedly been sharply criticised by Trump.

The president questioned US humanitarian assistance at the start of his second term and had numerous programmes shut down.

Under Trump, the world's largest economy also withdrew from several UN organisations and pulled out of UN-backed agreements.