USAID said the assistance was in addition to $100 million announced by President Joe Biden.
The US aid chief on Tuesday announced new support for the war-battered Gaza Strip on a visit to Egypt, as a renewed Israeli offensive again puts Palestinians at risk.
Samantha Power, the administrator of the US Agency for International Development, travelled to the Egyptian town of El-Arish, the gateway to Rafah, the border crossing that has been reopened but at limited capacity since the war started.
Power announced $21 million in new US assistance that will include hygiene and shelter supplies and food for people in Gaza, where water and other basics have been in short supply.
USAID said the assistance was in addition to $100 million announced by President Joe Biden on October 18.
Power accompanied the delivery by the US military of another 16.3 metric tonnes (36,000 pounds) of previously announced assistance that includes medical supplies, winter clothing and emergency food.
"The United States continues to work around the clock to overcome diplomatic and operational hurdles for humanitarian access, present solutions to emerging humanitarian assistance challenges and significantly scale up this response to where it needs to be," USAID said in a statement.
But the United States has also faced strong criticism in the Arab world for its military and diplomatic support of Israel, which has carried out a major offensive in response to an October 7 attack by Hamas, the Islamist militants who control the Gaza Strip.
The United States says it has pleaded with Israel to do more to protect civilians and to allow humanitarian assistance into the Gaza Strip.
The State Department said Monday that Israel, after US appeals, began to let badly needed fuel into the Gaza Strip.
Hamas militants launched an unprecedented attack on southern Israel on October 7, killing about 1,200 people, mostly civilians, and taking around 240 hostages, according to Israeli officials.
In response, Israel vowed to destroy Hamas and has carried out air strikes and a ground offensive that have killed around 15,900 people, mostly women and children, according to the Hamas-run health ministry.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)